TheRekindler

he new phone is a Google Pixel 5A. It still works in the old phone as well. 

Does it show "Telekom.de" in the top left corner on the lock screen? Can you make voice calls? I'm trying to find out if it is only data that fails or if the device is entirely unable to connect to the network.

Is this a new device, fresh from the factory, or did you buy it second hand? If second hand, has the phone been reset to factory settings?

Can you check if an APN profile is selected (and if so, which is selected)? The easiest way to get to that setting is by typing "access poiont" into the search bar in  settings, then click on the only search result "Access Point Names" and then again on "Access Point Names". This should take you to a screen that looks like the one attached. Make sure that either "internet.telekom" or "internet.v6.telekom" is selected.

Feel free to ask again if this does not make any sense or does not work.

Okay so checking, it shows Telekom.de in the top left corner. I attached a screen shot of the APN and it only has the internet.v6.telekom. We had bought the phone second hand but the phone had been factory reset when we got it. I'm not able to make voice calls except on apps like WhatsApp. 

Can you make those WhatsApp calls via mobile or does it only work via wifi? If WhatApp works via mobile, then mobile data would obviously be working.

It wold be helpful if you could upload a screenshot from the android diagnostics screen. The screen is available via a chatcode:

1. Open the phone keypad and type *#*#4636#*#*" ("*#*#INFO#*#*). This should take you to a screen titled "Test" with three options, click on "Phone information".

2. Scroll down about half way and click the "RUN PING TEST" button.

2. The phone info screen should look like the example attached from my phone (my phone is a Pixel 6, so should be similar to yours). Please take as many screenshots as needed to capture the entire Phone info screen.

3. For data privacy reasons, use an image editor to to erase all personal information from the screenshots (i.e. your IMEI , IMSI and phone number in the upper part of the screen and the TAC and CID numbers further down).

4. Upload the  screenshots here

This Phone info screen contains information on the attach status to the mobile network of your phone, data service, whether VoLTE is enabled etc, hopefully this gets us closer to the problem.