Mobile phone contract?

Have upgraded my mobile phone contract with a different monthly tarrif and extended term. however the phone which i was advised would meet my needs does not.the shop where i signed the contract 7 days ago, have said that only new customers get the right to change their mind and existing customers dont! does that stand even if it is new terms and conditions on a contract?the new contract itself would not bother me - it is the phone which is not meeting my needs.
Answer
You will have to wait the long 2 year period srry because our phones are not meeting their needs and we cant get out of our contract and ours end next month that is how life is you will have to deal with it