Why is my Galaxy s5 on Straight Talk not able to hold a 4g LTE signal

[AC Question]

I have had this phone for almost a year and have not had this issue until a month ago when I refilled my service and updated my service *228 or whatever number that is you have to call. Anyway, after that, my phone started dropping off to 3g. I can restart it and it goes back to 4g LTE but after a few minutes it goes back. Straight Talk was absolutely no help. Basically told to be happy that I had data.

 

[Rukbat]

On which carrier? (ST is a virtual network operator, not a carrier - it's probably on Verizon, but it could be on Sprint.)

*228 doesn't update your "service", it updates your PRL (preferred roaming list) or is used to activate a new phone. If you're in your home area, *228 usually doesn't do anything to a phone that's already in service. (It updates the PRL, but since you're not roaming, it's never looked at.)