4g is working but there is no LTE option available in phone

My 4G was working fine on the Vodafone network while I was in Qatar but after my return to home country I was unable to use the 4G as there was no option available to select LTE from settings.

However, when I took it to the market to get it fixed, the shop guy did some changes and 4G started working. I checked the speed from speedtest as well which turned out to be just fine. When I went to settings to select 3G to save battery, I was surprised to see that there was no option to select 4G in settings still.

I asked him for which he said that he did some tweaks and 4G should work fine but you should not change any network settings.

I need to ask what changes did he make to get the 4G working in such case.
Please excuse if my question is foolish but I am still surprised.

Thanks for the support.!