3 problem what are my rights

dekaspace

I got my PAC code a few weeks back but went away the next day for a week then had guests staying and I dont have home internet so not much chance to check.

3 constantly phoned me and offered me better and better offers, I am paying £35 a month currently and the contract runs out on the 16th(well thats the 30 days notice think my payment date is around the 9th)

Eventually they rang me back and offered me a new phone, and my current tariff for £15 a month inc VAT the phone they offered was worth a lot of money(about £250 new) so I agreed as its cheaper than getting a sim only and having limited minutes etc.

I went into bank yesterday to find they took out £50 plus another £15 and £5, the £5 was for the mobile broadband but the thing is I am already £20 in credit with them! and the invoice for the BB said "you dont need to pay anything due to being in credit"

I rang up and wouldnt explain what the £50 is for, nor why in the 7 months since I have had it everytime I cancel the phone insurance with them and bank they reinstate it and bank wont help me!

So instead of the £15 I was expecting to come out they have taken £50, I assume what they have done is charge me the £35 for the old tarriff and £15 for the new instead of just changing it.