Q: how to delete a number i dont want to be reached at off imessage

Hello phajjahines,

Thank you for using Apple Support Communities. 

I am understanding that you want to quit receiving Messages on a particular phone number. There are a couple of options depending on exactly what you want to do. See the following article:

Link your iPhone number and Apple ID to use iMessage and FaceTime

If you have multiple phone numbers that you receive messages you want to be reached at, see the section "Get started on your Mac" and uncheck the numbers you don't want to receive messages for. 

If you don't want to receive messages for the number for your iPhone, see the section "Unlink your phone number associated with your Apple ID".

Regards