return of cell phone

i did an upgrade telephonic at the upgrade dept. i was change to another contract which i still don't know what it is . i received a Nokia lumuna which i did not want , i received the phone in july 2015 .i have phoned them to return the phone in the seven day period after quite a lot of phone calls and go in to canal walk customer care shop the phone is still in my possession. i cannot get out of the contract till the phone has been pickup by ram at my premises. i have since stop paying the account but nothing is happening about that either. my number is