Alternative Method of Merging Accounts 

You need to sign up to the Seller Central Accounts with your valid Email Address and password.  Sign in to the account Click on the option of ‘Global Accounts’Click on ‘Merge Accounts’Follow the terms and conditions provided on that webpage Select the two accounts which you want to mergeEnter the details of the second account which you want to merge to sign in to that account as well. Confirm and accept the terms provided by the Company

Finally, your seller accounts will get merged successfully and can handle the accounts together for future use 

Conclusion 

Can I unmerge my accounts later? 

Once the Seller accounts are merged, you cannot unmerge them. It is a permanent change in the account settings.