This is primary caused by the Internet connection. If you don't have a fast and stable connection, then you might experience cut outs or hangups with the video. It doesn't matter if your connection is powerful enough, because it depends on the Internet from the other party as well. You need to tell them to connect to a faster source of Internet and then the quality will improve greatly, but given the fact it's Nigeria, don't expect much of an improvement since the Internet quality in the area is very bad.
