ARCELI Smallest SIM800L GPRS GSM Breakout Module Quad-band 850/900/1800/1900MHz SIM Card Slot Onboard With Antenna 3.7~4.2V

After hours of messing around at the recommended 4.1v it kept restarting, I bumped the voltage to 4.4v and now it works fine. Used a Vodafone SIM. It's needs to be able to source 2amps when connecting and transmitting.Documentation says 4.4v is the maximum but I've seen people on youtube running them at 5v, I've not tried this.

Good job done

I bought it and I will use it in the future for sure