Merging two accounts is simple. Simply log in to one of your accounts. Head to App Settings > Click on Edit Profile > Add the email ID or phone number of the other account > Click on Save. That will combine both the account details under one account. You can use any of these credentials to log into your JioSaavn account.
You'll be able to do the same by logging into the website www.jiosaavn.com. Head to Account Settings > Edit Profile to edit the details > click on Save.
Note: You won't be able to merge same type of details like two email IDs accounts.