Forum tip: I assume you're replying to these posts using your phone's email app - your email signature contains all your contact details which are posting to the open internet every time you reply. That's an open invitation for spammers to contact you unless the site admins edit your posts first.
I suspect your phone is using WiFi-calling, and you are on the border of usable mobile coverage thus causing handovers between the mobile network & WiFi. These are perfectly normal, but should not cause dropped calls.
Are you using Android or Apple? Some Android phones give you the option of "mobile-preferred" or "WiFi-preferred" which gives scope for troubleshooting. Does your phone show good mobile coverage when calls drop?
