I have a ZTE Swift Plus net setter, I used it in 3g network it works fine but recently I go to a remote place and I switched my network selection to GSM Only option but when I turn it to GSM it show 'No Service', I googled this and I found out some samsung phone has this issue and it can be solve by resting they called it as 'spt box'. I don't how to do it in ZTE.

Thank you,