Web3JS Transactions – How to Send Transaction to Call Function in Contract

It is the first time I do this so I have no idea what I am doing !
I am trying to call a contract's function and post data to it, this contract will then create another contract. Here is my contract how my contract looks like:

contract MedicalStaffObject {
    using strings for *;
    event LogCreatedTrip(address);

    struct medicalStaffDetails {
       string phoneNumber;
       string physicalAddress;
    }

    medicalStaffDetails public details;
    address[] public trips;
    address public orgAddresses; 

    function MedicalStaffObject (address orgAddress, string phoneNumber, string physicalAddress){
        details.phoneNumber = phoneNumber;
        details.physicalAddress = physicalAddress;
        orgAddresses = orgAddress;
    }

    function getDetails() public constant returns (string, string, address){
        return (details.phoneNumber, details.physicalAddress, orgAddresses);
    }

    function getTrips() public constant returns (address[]){
        return (trips);
    }

    function newTrip(address zone1, address zone2, address zone3, address zone4, bytes32 name, bytes32 startingDate, uint duration) public returns(address){
        TripObject newTrip = new TripObject(zone1, zone2, zone3, zone4, name, startingDate, duration);
        trips.push(newTrip);
        LogCreatedTrip(newTrip);
        return newTrip;
    }
}

And I am trying to call the function newTrip using this code in my NodeJS app:

 var web3 = new Web3();
    web3.setProvider(new web3.providers.HttpProvider(provider));
    var zonesTrimed = zones.slice(1, -1);
    var zonesArray = zonesTrimed.split(",");

    var contractAbi = web3.eth.contract(ethContracts.abiMedicalStaffObject);
    var myContract = contractAbi.at(address);
    // suppose you want to call a function named newTrip of myContract
    var getData = myContract.newTrip.getData(zonesArray[0], zonesArray[1], zonesArray[2], zonesArray[3], name, startDate, duration);
    //finally paas this data parameter to send Transaction
    web3.eth.sendTransaction({to:address, from:organisationWallet, data: getData});

However it just doesnt work and I keep getting this error:

Error: unknown account

First of all what does this error mean, does it mean it cann't find the 'to' or the 'from' account ? What I am supposed to put in there ?