The coverage guarantee  is only if you are on jump on demand (Lease), the promo for the iPhone 11 required eip so you wouldn’t qualify for the coverage guarantee unfortunately.

https://support.t-mobile.com/docs/DOC-23903

Hey everyone

We switched from Verizon to T-Mobile about 2 weeks ago and have been having issues with the network. I saw the Lifetime Coverage Guarantee, but I’m not entirely sure how it works.

We paid off 1 phone on Get out of the red and traded in 2 iPhone 7s for the iPhone 11 on Us promo. Would the coverage guarantee pay us like the full price of the phone or including trade in or something else?

I’m not for sure switching, but I’d just like to know what my options are.