This information could change your internet connection for the better, and not only apply to Denmark but could be used in your country too:
For years now I have only been able to get 3G where I live in Denmark, eventhough I'm surrounded by Mobile towers. Even after an extensive troubleshooting with my ISP(Internet supplier) they said that I lived too far from the tower.
It turns out, that is not always the reason for the problem - If you like me, have had the same Sim card and phone number for many years, then you Sim card may not be LTE/4G enabled!
This is something that support don't usually think about when they try to find the reason that you can't get LTE/4G.
You will need a new LTE/4G enabled sim card - if you are on Postpaid plan, then you can get one with the same number for free, but if you are Prepaid you might have to pay for a new Sim card and thereby get a new number.
Please be aware to backup your contacts before swapping out the simcards.
You can get APP's for making backup to your SD card or copy all your contacts to the phone, there is also an option to upload all your contacts to Google if you use an Android phone, just be aware that Google use a strange format for contacts so they might look a bit strange when restored(not always) - and you will need an internet connection for this.
Hope this helps someone.