Constant error during activation of facetime & iMessage on new iPhone Pro 13

hi there,

i just upgraded from my old iphone X to my new iphone pro 13 and i am unable to activate facetime and imessage with my phone number (it works with my email-address though). the error message i receive: "there is an error during activation. please try again."

first i copied all files & settings from the old iphone X to my new phone. since the error popped up using wifi and LTE i erased everything and setup my iphone pro 13 as new phone without itunes backup restore. still the same error message during activation.

i called apple support and also my network provider support but they blamed each other for the issue and could not help me at all.

facetime and imessage worked without any issues on my old iphone X so i am pretty sure there is no issue with my provider going on.

since i also removed the phone number from my itunes-account and re-added it later i am out of any possible solutions. Maybe someone has an idea what i could have missed?

iphone pro 13 has the latest OS updates btw.

Thanks for any help!