Follow the below procedure to transfer MTN MB from one SIM to another.

1. Dial *131*2 on your phone where you have the mega byte bundle to transfer

2. A message will be sent to you, just click reply and enter

3,after that, choose the amount of datas you'll like to transfer and enter the number you are sending it to.

If it requests for code put 0000 or your personal transferring pin if you've changed it previously.

I hope this tip did help solve your need. Feel free to let us know. Cheers.