Not registered on network

Been a customer for 2 years with no problems until 4 days ago when my lg g6 showed emergency calls only. Tried the sim in different phones but same problem. Called ID who said technical services would be in touch in 48 hours, they weren't, so called again. I'd recently upgraded, so I had a new unused sim, was told to put it in and they activated it, but 2 days later I'm still not registered on the network. Like most people I depend on my phone for business and family communication. My son fell of his bike and was unable to contact me. By the way he has an ID sim which works fine. I see that I'm not the only one to have this problem, I'm looking for a more reliable network now, but just wondering if anyone knows what's going on ?