Instead of helping me, the service person offered to return the phone for a refund.
Never mind, I rooted the phone and fixed the problem myself by editing apns-conf.xml and adding the missing MMSC information. I can now send and receive MMS messages on the 4G network.
But I shouldn’t have had to do that.
I am very disappointed in Blackview’s after-market support. Not only did they not understand the problem after my having explained it clearly a number of times and provided settings and videos of the problem, a complete analysis, and what to do to fix it, they asked the same questions over and over again. I do not even believe they passed this information on to the software engineers that are working on the android O/S of the phone.
I will definitely think twice about purchasing another phone from Blackview in the future.