For warranty claims, they can be processed by the telcos only, no where else. And any centre/branch will do.

Whilst your statement is not entirely incorrect, it is also not right. If there is a defect especially if it affects the functioning/performance of the unit, you can send in for a warranty claim.

AFAIK so long as the unit is within the warranty period and if it is defective, you can send in for warranty claim until the period runs out.

Can I just correct you a little? You may not get a new set. Highly probable that it would be a refurbished unit.

The trend or perhaps I should say practice thus far is that most if not all replacement units are refurbished. The exception would be that when one sends in a phone for warranty, a new 'model' is just launched which Apple then would not have any refurbished units available, he/she would get a new set.

Most of the refurbished units are of US origin and therefore by referring to the Part No. which would be a US one, you would know that it is refurbished but it would be officially unlocked.

The prerogative is the carrier's. But generally, they will replace 1 for 1. In any event you are assured that your problem will be addressed and solved either way. So, just send it in for a warranty claim.

On the positive side, at least your predicament arose whilst it is within the warranty period. Some, I know, was past it and therefore had to fork out their own money to have it repaired.