Pixel 2, Android 11. Hadn't done any changes myself, issue just started out of the blue in August. Thank you for the additional links - I had done most of the troubleshooting in them already but the first Verizon link suggested resetting the network settings. Didn't want to lose all my existing wifi setups but finally did and after rebooting tested calling out to several different numbers. No issues! I haven't used my phone for more than about 5 minutes yet so can't confirm that calls are no longer dropping due to the 'server error' but will update here after my next longer call.