Hi, you can always check your call history via Your MTN smart web account.
Just use this link to logon to your account: https://mymtn.com.ng/login
Under History, you will see...
I bought a Mifi device from your shop at Ikeja City mall
S/N 320513884549
IMEI: 867462052329632
and MTN line 08104170681
and I was told I will get twice the data I purchase...
From my own experience using the MTN 4G Mifi device, the 100% bonus data offer is real, provided you purchase data bundles from N3,500 to N20,000 for 6 months on the new SIM...