You are not writing very clearly. What do you mean by your 'actual number'? How have yoy got two different numbers? Did you already have an o2 number before you bought the simplicity? Are you using the sim card supplied with the new plan?
The first thing to try would be to pull the battery out of the phone while its turned on, then take out the sim and wipe it with a soft dry cloth, then replace both and restart the phone.
After that try calling from a different phone and see if yours rings, this battery pull allows the sim to reset itself. If that doesnt do it speak to o2 and get them to check the port went through completely.
It also reads like you are being a bit sarky with me, theres no need to be rude when someone is trying to help.