MacOs 15 Help

I just updated my Macbook Pro to MacOs 15.2 and now my iMessages on my laptop are screwed up. I'm an American living in England and I still use my American phone (iPhone 8) to keep in touch with family/friends and it's also the phone I use for work. I work for an American company. I also have a UK phone (iPhone 11). Once I updated my Mac to MacOs 15.2, the iMessages either want to send messages as my iCloud email or my UK number. My American number is not showing up as an option on my laptop. Since I work with American colleagues, I don't want to send them messages from my UK number. I would assume they would get charged for messaging an international number. But I also don't want my contact name to come up as an email. I just want my regular American number to show up. This probably all sounds confusing, but does anyone know how I could fix this? Any suggestions?