How to prevent watch from connecting to the wrong devices?

I have multiple devices, all with BT active for different reasons, all with Garmin Connect installed so I can check my stats there too.

Problem is, the watch now also gets connected with them, even though I never did the pairing on all the others.

What can I do so that the watch to just connects to my one phone. Disabling BT or uninstalling GC on the other devices is not a valid solution or answer to this question.