deactivating number

Is there anyway I can deactivate the number to my phone (because my carrier will not let me) so I can go use it with another carrier?

Don't deactivate the number. Go to your new carrier, start your account and tell them you want to "port" your old number to this new line. The line must be active on the old carrier to port it. Once the port request goes through, it will automatically cancel your old line at your old carrier.

Will it cancel the whole old account with the old company? Also what if it's not my number originally I bought this phone off Kijiji

If you only have the one line, it will cancel it all. If it's one line out of several, just this line. If you will owe an ETF when you cancel, they'll tack it onto your final bill.

If this is the number you are currently using, then it is basically yours to move with you.

And make sure that your account is current (meaning that you have paid your bill).

Sounds like the OP is talking about releasing the PIN. The original owner will need to contact their provider at the time and have them release the PIN. RIM will not do it as I understand.

We may need a little more clarification since we have 2 distinct possibilities here.