Last month, I moved from Vodafone to Telekom, I transferred also my phone number. I received the new SIM card last week (29.9) and started to use my new contract (the old one with Vodafone expires soon) by switching the sim cards in my phone (Pixel 6 Pro).

I didn't experience any problems, was able to call or receive/send SMS or RSC messages (from Telekom or my friends). But I realized I am not able to login to some services which require 2-factor authentication and sadly only the SMS method. So far I recognize 2 different services. No verification message received from Sentry (comes from US number) or AVI Medical (Hausarztpraxis, number not visible).

I double-checked all settings which were suggested across the forum or FAQ ( APN , SMSC) and all correctly set. 

I suspect, this has something to do with the change of mobile operators as until last day with Vodafone, I was able to receive those messages.