If the watch is connected to your phone via Bluetooth, you can “make calls” in the same way you could make calls with any other Bluetooth accessory such as headphones or a car stereo

Text messages should just work as well, same basic idea

I would say from a 5, if you don’t just want a new battery, grab a Series 8/9. Keep an eye out for Black Friday deals.

Obviously a new battery is cheaper but a newer watch will get updates for much longer (duh) so that’s really between you and your wallet