I believe you can have multiple phone numbers associated with your iCloud account if they are a physical number. This is assuming you have a phone that's capable of dual-sim or if you have a second iPhone linked to your iCloud account. The latter is what I do when to make myself available when traveling abroad.
I have a dual sim iPhone 11. Everytime I switch off the main sim and use the other on abroad, imessage breaks and I have to use WhatsApp. Never manages to link two phone numbers, less so to use it without the correct sim...
I believe you can have multiple phone numbers associated with your iCloud account if they are a physical number. This is assuming you have a phone that's capable of dual-sim or if you have a second iPhone linked to your iCloud account. The latter is what I do when to make myself available when traveling abroad.