There are few things you know know about 4g and it is about its frequency. To use 4g your phone should be compatible with the frequency of Bhutan telecom. mos people they simply get a new phone having no knowledge about the phone where it would support 4g in your country.
If you are getting a new phone please don't miss the chance to see if it support 4g.
2g/GSM supports 900 hrz
3g/WDCMA supports 850 hrz
4g/lte supports 1800 hrz
If you have a phone with different hrz then your phone will not work in Bhutan. before you buy a new phone please check its hrz. The hrz will be given on the box of the phone it looks something like this.
