Money doesn't grow on trees!!!

So my contract ends on the 23rd of May. Called through to cancel it a while back but was convinced otherwise and took out a 10GB data contract, which will only come into effect once my contract ends and I can still cancel it incase I change my mind, which I have now. Firstly, every department answers the phone, but you never get through to cancelations, I tried the whole week. Then I hear there was a strike, I guess only that department got affected. Now my contract hasn't ended and they have opened my line and removed my out of bundle limit and my usage keeps increasing. The explanation that I got was that with the new contract, I didn't set a limit. I would accept that except it's not in effect yet, and if it were, where is my 10GB data? How can I jump to usage before I even receive my monthly data?

Very upset.