I just went through this. For Galaxy Watch 5 and above (and potentially 4) you CANNOT do what the OP is intending, i.e., manage a standalone Galaxy Watch 6 from your existing (parent) phone on the Verizon network. Rumors are that you can from other providers like T-Mobile but Verizon is 100% no go.
I went in circles for days over this and ultimately purchased a cheap $99 (ok not cheap) phone at BB to manage my kids watch. This ultimately proved to be the easier solution.
I tried a million things and I'm very tech savvy. Suffice it to say everthing I did had to be untangled with a 90 minute phone call to Verizon. This included switching the SIM card in my phone to match the SIM of my childs account, trying other phones in my home (too old) and a LOT of verizonwireless.com moving of plans and devices. Nothing worked and only made matters worse.
In any event, the separate phone is a more graceful way to do this becuase everything my child does on the watch is viewable from the phone. I can see messages, location, email, etc. I'm not that much of a snoop but I need to keep an eye on SCAM texts, emails, etc. and this works better. I can link some of the functions to my own phone to make this easier but mostly I need to manage his watch from the second phone.
Good luck to you all. This is NOT simple on Galaxy Watch.
