Prepay meters and need to find out my Mpn or meter number

Also, I have an issue with my gas meter saying I’ve used my emergency credit and I haven’t. As that would mean I’d used 25 pound of gas in 5 days. I don’t think I have used that much at all and I certainly haven’t put the emergency credit on. So where has it gone. Need my MPRN. number to look at other companies and how I can get a better deal and I can’t seem to figure out how to find it since I’m on prepayment Meters I don’t get bills and we don’t have the app available so I’m stuck