Well that stinks! And also, the rep is not telling you the truth that somehow old phones will handle the 1x service better. If anything, with each device that comes out, there are more bands inside the phone increasing connectivity stability.
You're in a bit of pinch since 5G is way off, like year 2020 off! Here is what I recommend. Are you struggling with calls at home mostly? In that case, there is some hope! You can get a signal booster that should alleviate some of that headache. I would call Verizon CS and demand they give you this for free since they have no intention of fixing your service. That at least would solve connectivity there.
https://forums.imore.com/e?link=http...token=bfOr78je
Wi-Fi calling is another option (thanks community).
How was service on the 6s before? Obviously it was more reliable, but i'm assuming you were probably not getting LTE around town?
The other thing you can try this is very basis is:
Settings app > Scroll till you can tap on General > Scroll to the bottom and tap on reset > Tap on "
Reset network settings. Just be careful when you do this because you could erase your entire phone if you are trying to do this quickly! Just trying to warn ya

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