USSD code or SMS, in both cases you still have to slot in your sim into a mobile phone.

hi, i explain it for you, you pay your bill with me ya  got discount oh
u paid RM 50 advance fee, so the balance of advance would be RM 38 ( u should pay 1 month deposit)
stamp duty RM 10
so ur first bill minimum amount would be RM 48
so 113.6 -48 = 65.6

A/ 28  * 88 - 10 (rebate) = 65.6
A =  24

28-24+1 = 5,  so it means u subscribe the package @ 5th of February
usage = 24 days, the complete calculation is 24/28 (prorated)  * 88 - 10 (rebate) = 65.6

so your bill 65.6 + 48 = 113.6

this amount already cleared your FEB bill and also MAR bill ( because u paid advance )
so basically you paid 50 + 113.6 for 1 month and 24 days, make sense ?
sorry for poor explanation 

You paid advance 50 during registration remember?
So you only need to pay extra 38 to make it total 88 for your 1 month advance payment
And first time stamp duty 10

So is 48