Primary Consideration

Due to the controversial nature that this specific problem represents, it takes a mature player and a mature DM to handle this specific scenario well. Ensure that the player and DM have a conversation about something of the magnitude of power revocation BEFORE it is implemented in play...

If you are the DM and this is established as part of your world, ensure that players know this up front if they are considering playing a warlock (or any other class likely to have powers revoked for any reason).

If you are a player and you want this to either be highly probable, talk with your DM. It can create an intriguing story.

Already covered

RAW, there isn't any explicit text that covers a warlock's powers being stripped. Also, there is no class that has rules text covering a loss of powers, save the Paladin whose powers change form when he becomes an Oathbreaker. (DMG p. 97)

Lore from stories associated with various pact-style magic demonstrates and sets precedent that it could be a good story hook, allowing for a very interesting story line that leads to all the things that were mentioned in the original question.

Also Consider

The power belongs to the entity to dole out. If they granted it, it is likely true that they could take it away. This is more of a reference to old literature, to what makes sense, and to what would be fun with the game you and your DM seem to be trying to build.

The rules do not state the specific pact, this is the part that cannot be stressed enough. The power that they currently have should mostly be considered as payment for services rendered. If they are not completely paid for (ongoing payment, for example), then try to avoid stripping a lot of their power from them. Make it minimal, but noticeable. Lower spell slot levels by one levels as that part hasn't been paid in full, if that helps the story line, but do not completely cripple the character.

As for the specific scenario posted in the question:

The devil is highly unlikely to strip power from someone if it is part of a contract. To do so is highly unorthodox for a devil, and would be looked at even more poorly than an upstart servant that the devil couldn't control. The devils live by their contracts, and although adding loop-holes may be favored, rescinding an agreement is not. If a devil were to rescind the power of one of their warlocks, it is likely that another entity would try to mock them by taking the contract instead. This is even more true of a relatively powerful warlock. That said, a devil is also very likely to add a hidden clause that prevents the warlock from using their powers against the devil, with revocation of powers being either temporary or permanent, depending on the devil, the warlock, and the devil's disposition at the time.

They will follow the letter of the contract completely, but don't care about the spirit of the contract. If the devil is powerful enough to grant powers as a patron, they are likely intelligent enough to be more careful about the contract, though a particularly savvy and/or intelligent character could manipulate them in to a contract that is written to the benefit of the character more than the patron (protecting themselves from abandoning the patron, for example).

If you really want to do it

The best way to add the possibility of power revocation for story-line purposes is to ensure that it is an active part of the party's story (as opposed to a passive one). Allow the party to try to stop the powers from getting revoked, or have another patron (possibly a more sinister one) inform the warlock that they are going to lose their powers and offer to be a surrogate patron.

Do something that directly involves the warlock in whether they lose or retain their powers.

In short

Is it possible? Rules don't state that it is, but this is something a DM could easily say yes to with good justification to back it up based on game world.

Should the DM take this path? Probably not, or at least not seriously. If he does, then he should offer a work-around. Don't strip power from a character/player without offering a way of obtaining it again. Don't make the game less fun.

Your problem isn't that you need to persuade your GM to change how the Warlock class works. Your problem is that you've fallen prey to what I'm going to start calling "the Nomenclature Bugbear."

Each character class is a collection of abilities built around a concept frequently found in works of fantasy fiction. These classes are given names, presumably because it gets awkward saying "I'm playing a person-who-uses-weapons-and-armour-really-competently!" all the time. For example, the fighter class can use armour and weapons well, and the wizard class uses magic and keeps spells in books. You'll have worked this out in a few minutes of reading the class descriptions.

However, being a member of a class doesn't mean your character identifies herself with the name of that class. A Fighter could be a Viking raider, a knight errant, a conquistador, or any of a thousand other possibilities. Similarly, there are loads of characters in fiction who cast spells and keep a library, and most of them aren't called "wizard." The Nomenclature Bugbear arises when we forget that class names are a convenience of game jargon and start thinking that they're recognised in-universe.

To be fair, this is an easy trap to fall into, as often the words used for class names do exist in-universe: They were taken from the fiction that inspires the game, and most campaign settings are also inspired by that same fiction. Most D&D settings do have people called wizards, and most of them are members of the wizard class, because the wizard class is pretty good at representing what wizards are in that setting. You just need to remember that in many such settings, in-universe nomenclature doesn't necessarily line up perfectly with the game terminology: In most settings, you can introduce yourself as a "thief" and people won't assume your character is a Rogue with the Thief archetype, because the only in-setting qualification to be a thief is to steal things, and any class can do that.

Getting back to your example...

You want to make a character who's a witch in the campaign universe, a person who uses subversive magic as an alternative to physical might and social prowess. You want this to be supported by the game mechanics and your GM. Those are reasonable goals. To achieve them, you need to do two things: (1) You want to find a class that fits with your concept, and (2) you want to work with your GM so that you have a shared understanding of what your witch is intended to be.

As your GM has pointed out, the warlock class isn't really what you're looking for. But your concept is still pretty broad, and that means it's flexible. With your GM's permission, you can simply pick any class that fits it, perhaps wizard, cleric, or - well, anything that uses magic - and have your character call herself a "witch" in conversation.

Once you've picked a class whose list of abilities sounds like your vision of a witch, explain your idea to your GM. It sounds like your GM doesn't object to your character's concept, so I expect he'll be receptive. As long as he agrees that there's no major dissonance between what your character can do and what she calls herself, you'll find that this solves your problem. It might take a bit of back-and-forth if he has existing nomenclature plans for magic-users in the setting, but eventually you'll have a character that you're happy with, and which your GM understands well. It's win-win!