T-mobile unlimited data?

Hi, everybody.

I'm planning to buy an android phone with unlimited data allowance, however, it's not directly from T-mobile but an online shop like dialaphone.co.uk or something similar.

Now, on the fair usage policy on the t-mobile site it says that android phones have up to 3GB of the unlimited data.

I was just wondering if the 3GB applies to all Android T-mobile contract phones bought anywhere or only the ones bought directly from T-mobile site or shop.

Thanks for every useful answer in advance.