Preferred Network: Global or Lte/Cdma?

I use mint mobile. Last year, my phone quit making calls saying "no sim card or sim card error" I ordered a new sim card from mint. In the meantime, I figured out the problem and got it fixed. However, when I got the new sim, it installed different APN settings that can't be edited, deleted or changed to a different APN. Now, for phone calls and texting, I have to have the mobile network set to "automatic". When texting pictures or web data, I have to set my phone to LTE/CDMA. If I forget to switch it back, I can't make calls or send text messages. I have 4 lines with Mint and it only happens on my main line. Did I mention that this is exceedingly annoying? Amy thoughts on situation? I have not called Mint about it. They used to be great with American agents, now when you call, you get someone in Philipines or India.