(Many students reported that they could not access the Internet after setting up their own APNs, they might be able to surf the Internet but could not receive MMS messages, or other problems. In fact, many of them were due to the disorder caused by adding three APNs: net, wap, and mms according to other tutorials! There is a problem with the method of 3 APNs, because the system will not automatically switch between wap and net, so only two apns can be set. Except for MMS, everything goes through cmnet. Now the tariffs of wap and net are basically the same.)