Learn English – “Call” vs. “Call at”

"On" refers to the medium:

Call me on my cell phone.
Call me on the walkie-talkie.

"At" refers to the destination:

Call me at home. (Using my home phone number.)
Call me at 800-555-1212. (The number serves as a target or destination.)

Of course, "on" and "at" can also have time-based meanings, but that doesn't seem to be what you're asking about.

In that sense, you can use 'by' with any tense. Consider its meaning as given by the Longman dictionary:

Before or not later than a particular time.

Examples:

• The document needs to be ready by next Friday.
• By the end of the day we had sold over 2000 tickets.
• By the time we got home we were tired and hungry.
• I'll be home by 9:30.
• Please try to have this done by Friday.

All the examples are borrowed from the Longman dict. so you can trust them.