Not sure if this will work but it is worth a try. Take the sim out of the dongle and put it in your mobile phone and dial *#100#
That should bring the number up on the screen.
If that does not work call 07836191191 (customer services). If you give them the number which is written on the SIM card they will be able to tell you what the mobile number is that is assigned to that SIM.
P1E EATER
"Promises and Pie crusts are made to be broken"