If your Android phone will not allow you to send and receive pictures, more than likely your problem is one of two things. The first I will show is a simple setting change. The second is a little harder but still getting settings straight. Each of these have worked for me on one of my phones. On my current Android S7 I had to use the second.
The first one is to go to settings, which is in apps, then go in mobile networks. Now make sure Mobile data and enhanced LTE services are on. If they are on and you still cannot send and receive pictures, go on to the second.
The second way is to set the Access Point Names correctly. Now go back to Access Point Names in Mobile Networks. What you probably want to do is search for APN for your phone and the network you are on. They will tell you the settings you should have. In my case I have a Samsung S7 on Straight talk which is using ATT thru Straight talk, but the setting is slightly different for Straight Talk. I created a new APN and got the settings correct. There will be an APN there, but you can choose to use the new one. Deleting the old or changing it was blocked on my phone.
I went to the following URL to get the settings the APN on my phone on Straight Talk. Remember search engines (Google, Yahoo, Bing, etc.) are your friend. Once I fixed the APN (Access Point Name) correctly, my new (new for me, really used) works like I had hoped.