Yes, you can. You will first need to convert all your MTN contracts to pre-paid. Once on prepaid you can sign up for Afrihost month to month (airtime & data ) or data only. During the signup process you will be asked, if you need to port your number, want to get a new number, get a new sim, need a device or if you are on MTN Prepaid. Select you are on MTN Prepaid.
The articles below will help you sign up:
How to sign up for Air Mobile Monthly - https://help.afrihost.com/topic/afrihost-mobile/how-to-sign-up-for-air-mobile-monthly
How to sign up for Air Mobile Data Only - https://help.afrihost.com/topic/afrihost-mobile/how-to-sign-up-for-air-mobile-data-only