I’m having trouble making calls using the SIM A7670C. Right now, it’s successfully connected to the Arduino Uno WiFi, but the power supply is still insufficient. I solved the power issue temporarily by using a power bank, which allows the module to detect the network signal, but it still can’t make calls. Plz help me 
T-T
What help do you want?
The module needs more power than your arduino uno wifi can provide. You need a dedicated power supply for the SIM A7670C, which is the solution your found.