Blacklist phone remover

Hello my name is [Edited: "Personal Information"]. I moved my line from T-mobile to Xfinity Mobile and I bought from Xfinity. Now my phone said it’s in blacklist I can use my phone no more. I don’t know what to do now can you help me please. IMEI number is [Edited: "Personal Information"] They trying crazy because of this issue. Please help me remove the blacklist from my phone thank you