Who I have the same questioned this topic

I recently returned from an overseas trip and now, when attempting to merge calls, the connection gets dropped for the original call and the call I am attempting to add.  Did not have this problem before the trip.  I used Verizon’s $10 per day while roaming in Costa Rica.  I have LTE set to both voice and data (tried data only which did not appear to make a difference) and have WiFi calling enabled. What gives?  I am in zip code 78735.