iPhone 4 home button inop and poor signal.

I have an iPhone 4, and my home button is (more often than not) inoperative, and also the signal is very poor, my calls get cut off and SMS won't send etc, I have had my phone to the genius bar where they 'cleaned the contacts' a couple months back and now it's back to the same as before if not worse, as it is not under warranty anymore or not covered by any apple care etc I understand the cost is down to me. The woman in store told me that if the fault persists they will exchange my phone for a reconditioned one at a cost, would I be able to pay extra/ pay more and get a white iPhone 4s instead of a black 4g which is what I have now? Thanks.