Forcing IP Whitelisting Globally
If you know the exact IP of the incoming MySQL users, you can do the following

Suppose the user is called datacustomer and the incoming user's IP is 10.200.210.252. From what you are saying, there should be a MySQL user within mysql.user called datacustomer@'%'. You cansee that user by running this query

SELECT * FROM mysql.user
WHERE user='datacustomer' AND host='%';


If one row appears, you can change the host of that user

UPDATE mysql.user
SET host='10.200.210.252'
WHERE user='datacustomer' AND host='%';
FLUSH PRIVILEGES;


You'll have to repeat these steps with every MySQL user.