Windows 10 store / Xbox account issue

Hello so iv been searching countless of times for a solution for this and i couldn't find anything so here is my questions and thanks you.

1-Can i change my old xbox live gamertag on windows 10 ? When i try to pay for it on the xbox website i can't change the billing region from US to my country OMAN which is weird because my Microsoft account on the windows store is set to my region and i
already bought a lot of games with no problem.

2-Can i change the xbox account that is tied with my Microsoft account with a new one so i can keep the games and save data?

I tried account migration already and my country of course is not listed i don't understand why Microsoft is complicating everything its 2019! They can easily avoid all these issues if they sell a gamertag change token or whatever on the windows store.

If nothing going to help me in this situation id appreciate if i can get some suggestions on what can i do?

:)