MMI errors, also known as Man-Machine Interface errors, occur when the following happens:
- The phone doesn't understand what you are trying to do.
- What you are trying to do is invalid (e.g. inputting the wrong activation codes).
- The phone is not subscribed to the service you are trying to perform (in this case, conditional call forwarding).
Prepaid carriers get the MMI error because setting up conditional call forwarding is not possible or an allowed feature for them. When conditional call forwarding should be working but it is not, it’s because the sim card doesn't understand that you are subscribed or allowed to perform that action.
Reach out to your carrier and let them know you are getting an MMI error when trying to set up the conditional call forwarding, also known as the busy, no answer unreachable call forwarding. They will be able to see what the issue might be or even set it up for you. All you need to do is provide them with the forwarding number assigned to you when creating your YouMail account!