I just came up with an idea of how to solve the problem of insufficient credit in activating the 7.5gb data for mtn.
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**The sim where you want to transfer the data to should be on the mtn ipulse plan
**The sim should have a minimum of about #100 on it
**With that #100, you should also have the 10mb and extra 5mb that mtn normally give on weekly basis for ipulse tariff users
**Then, you can now try transfering the data with that short code.... *131*3*5*4*3*the recipient number*ur pin#...the recipient number is your number want to get the 7.5GB
**You would now receive a message saying you have gotten the 5gb and an extra 2.5gb.
**When you check your balance, you won't see the 5gb instead, you will see the 10mb, and the two extra datas, i.e 2.5gb and 5mb.
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I hope this works. Give it a try.