Mobile account

[Col68f]

Hello. I purchased a phone and sim a couple of month ago, when I was setting up the phone and sim I did a PAC code which then changed my number from the new sim number to my original number. A week or so ago it started playing up and for some reason it has changed my number on my iCloud account and mobile service to the number that first came with the phone. Please could you help me. 
thanks 

[caesarome]

@Col68f 

If this is an iphone refresh the network settings so go Settings > General > Transfer or Reset [Device] > Reset > Reset Network Settings. Then go to Settings - Phone - My Number and change it if it is wrong, then reboot the phone. You will need to set up your Wifi connection again.