Samsung S6 got hacked

[AC Question]

Somebody sent me an MMS to my Samsung S6 edge and I tried to download it but nothing would show up. I thought maybe it was just a buggy mms. Then I started noticing strange behaviours with it over the next few days...pictures being deleted, videos being taken (not by me), phone getting hot just sitting there. So I backed everything up on Google Drive and got myself the new Samsung S7 and synced it to my Google account. The same person tried to send me two more mms this time but I didn't download (even though I've read that mms hacks can self extract even if you don't download them, aka Stagefright). The same things started happening to my S7, so I factory reset and didn't back sync with my Google Drive and basically have a blank phone fresh from the box. So here I am with my S7 (with both WiFi and LTE off) and I was with the person who sent me the mms's and when my Dad sent my phone a text his phone vibrated literally like 10 seconds afterwards. Is it possible for somebody to have gotten hold of my carrier account information and compromised all of our phones as we have a family plan and have 3 phones attached to the account? I've changed all of my passwords for most of my accounts and the 3 members of my family all use androids whereas the person who I feel is compromising our phones is using an iPhone. I've changed sim cards multiple times but my number has stayed the same. This is really starting to bother me and any help would be greatly appreciated!!