You do not need PPP to poll a cell modem for position data.
PPP (called PPPoS in some environments to differentiate from PPPoE) is not AT commands. AT commands you need to init your cell modem and put it in PPP mode, that is all that is related to it.
If you want to connect to the cellular network and that is not working, you need to check your setup. You will need the proper dial number (which is almost always the default) and your APN, user and passowrd. Those belong to your provider.
The post I mentioned in the chat is this one, you should search for others perhaps more relevant to your particular problem.
If you want to poll the cell modem for position data (be it GPS, GNSS, or whatever), you have to send the proper AT command through the serial port and listen for the incoming response and parse it. You do not need PPP.
However, if you want to do both, you are in trouble since PPP will take over your serial port and that will require more effort. I can’t help there.