my iphone 6 keeps saying sim not supported at activation screen can someone please help me?

Hi

This means that the iPhone is locked to another network provider only they can remove the simlock Contact them.

Cheers

Brian 🇬-1F1E7;

It means the iPhone is locked to the previous provider. They are the only one who can officially unlock and if you qualify.

If it's second hand iPhone, return for a refund.