Q: trying to update my mobile phone number on apple ID keep getting told to enter a valid number any suggestions please

Hello dave-t13,

I apologize, I'm a bit unclear on exactly what you are describing. If you are talking about changing the phone number associated with your Apple ID for things like iMessage and FaceTime, you may find the information and steps outlined in the following article helpful:

iOS and OS X: Link your phone number and Apple ID for use with FaceTime and iMessage - Apple Support

Regards