Who should i ask to merge accounts, cause the following is not helping
Merging Microsoft accounts isn't an option, I'm afraid. What you can do is close one account, or simply stop using it which will close it permanently after some time (two years, I believe).
However, if the accounts appear to be linked already, maybe these are in fact two mail addresses signing in to one and the same account. This is called having an alias.
You also mentioned sign-in issues. Are you saying that you can't sign in even on the web, at https://account.microsoft.com, in a private browser window?