.
I've got a wild suggestion for that, but I'm not sure if you're gonna like it.
Here goes nothing:
Top-up with Rs.20 (Talktime 14.95)
Top-up with Rs.10 (Talktime 7.47)
Now your main balance will become,
30 + 14.95 + 7.47 = 52.42
Now you can try activating 48 pack via USSD again. May be you'll get two Rs.48 packs running simultaneously? 6GB in total?
After this, your remaining Main Balance will become,
52.42 - 48 = 4.42
I know. This idea expects you to spend 30 bucks in order to utilize the 30 bucks you already have as main balance.
For now, that is all I could come up with though!