To release your withheld number in the US so that you can call someone who does not accept withheld numbers you may first need to dial the prefix *82 followed by the persons number who you want to call.
This must be used to call the number with every individual call that you make to the number which does not accept withheld numbers.
It's likely that you requested your personal number be withheld when you arranged your call plan with your network operator so if you require your number to be revealed long term it may be best to contact them so that they can arrange this for you.
Releasing your number in the UK
If you wish to release your number in the UK before calling a number that does not accept withheld numbers, you should first dial the prefix 1470, followed immediately by the recipients number.