My line just got deactivated, how do I reactivate my line without visiting any mtn outlet.

Hi, Yusuf. MTN does not have provision for online SIM retrieval at the moment, you must visit their office to retrieve your line.
You can dial *123*7*1# to get information on the location of any of their shops closer to you.
When you dial the code, you will be required to enter your State, then your Local Government Area, you will receive SMS on the nearest MTN office address in your location, or you can use this link: https://www.mtnonline.com/personal/find-a-store/