In your case, the system is very unfair.
Did you hear this from the shop/telco or from Apple? You need to
call AppleCare and speak to a rep, tell them your story and they
will write a case. They will grant instructions to the shop/telco
to give you a new phone, quote your case number to the shop. That's
how Apple's customer service works. Usually the shops have no
balls, no brains or both. Leave it to the shops and Apple's brand
will be ruined.