Doorbell call quality over 4G affected by phone wifi setting

Summary: Phone Wifi ON setting is causing poor Ring Doorbell call quality if house wifi out of range, but OFF setting works OK?! Can anyone help with this issue? If I am out of range of my wifi (hence just getting a 4G signal), BUT if the wifi setting on my phone is still ON, I get extremely poor quality of the doorbell is rung and I answer on my phone (I get no video or sound and the person at the door gets something that sounds like a few burbles but cannot here my voice. If I repeat the test, but with my phones wifi settings turned OFF, then I get good quality video and sound. I conclude that my phone’s attempts to locate a wifi signal is causing poor quality over my 4G connection but has anyone experienced the same issue? And if so, apart from leaving wifi OFF on my phone when I am out of the house, what can be done about it? Thanks in advance for any help, Gray