Re: When I get facetime calls, I only get them on 1 iphone (11) and it's not the one I always have with me
You may want to try going to Settings > FaceTime:
Below “You can be reached by FaceTime at,” you might enter your other phone number, if you haven’t already.
You might want to experiment with both phones listed, and / or with just the one you always have with you.
NB: Check you also have the phone number(s) you want to use for FaceTime listed on your own Contacts card(s) in your Contacts app. Eg: Add or edit your contact info and photo on iPhone - Apple Support
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Re: Can I choose which device get the calls or can I can make sure they both get them?
Sorry I don't know: Whichever device(s) you decide to list in settings (and on your Contacts card) makes a difference, and that gives you some control. Also: whenever both phones are handy you may be able to: Hand off a FaceTime call from your iPhone to your other Apple devices - Apple Support