Return Service Requested - credit letter

Hi, I've purchased a phone and a monthly service online 

and I'm a current xfinity internet user. 

After the purchase, I received the phone with sim card a few days ago.

But today, I've just received a letter from Xfinity Mobile saying the you decided to deny my request

or offer me substantially different products and such based on ___. 

I've checked my page and it allows me to activate the phone and start using. 

So I don't understand why I'm getting this letter at all.

Could someone please clarify and explain why?

Thanks,