I have been usign my iphone 6 as well...I really had to adjust my setup to reduce the oops network outages. Now, they are fewer outages that I deal with. :-)
1. I relocated my 2.4 ghz wireless access point (same room I sit in) close enough I can throw a nerf ball at it.
2. backed up the game to facebook, apple, etc. so if I delete I won't loose everything.
3. deleted & re-installed the game.
4. clear out any web browser data on phone.
5. I set the game to NOT use cell data. I only play MM20 while in house connected to my wi-fi.
From my years of experience there are multiple possible area's of data congestion. But, all I can do is check my end & if EA can check there end as well.