SIM Card not working on RAK7249

Issue: I bought this gateway recently and inserted T-Mobile sim card for Cellular data however, there is no IP address assigned but I could see the operator and other info. I tried disabling WAN, WiFi AP mode for cellular connectivity but none worked. This is the error quectel-CM[28855]: requestRegistrationState2 MCC: 310, MNC: 260, PS: Attached, DataCap: LTE quectel-CM[28855]: requestSetupDataCall QMUXResult = 0x1, QMUXError = 0xe

I tried to get into the AT command interface but I couldn’t find any documentation to access quectel module. Hopefully somebody could help me out