Network question 4g/3g

[antoniotaj]

So recently I did the fdr and my battery life increased and disabled apps and i downloaded lte on/off and my 4g worked fine and everything even though i mainly use cdma when out of the house but now when i try to change my cdma to lte it says it.changed but the network will only show gray bars no 3g or anything and.i cant.connect to the internet at all so now im stuck on 3g auto any help would be great ive turned my phone on and off but nothing has changed