Vodafone India — Data balance deduction

Address:	Kolkata, West Bengal, 700147
Website:	www.vodafone.in

I recharged a 2g data plan of rs. 179/- on 11th december 2016 and i was using as 3g on special offer. Which has a validity till 7th january, today. Again on 3rd january i recharged with a 247/- data plan (Validity till[protected] because i had only 93.69 mb data left related to my previous recharge.
Now all my data usage deduction is happening from the second data balance since i've done the 2nd recharge, even when my handset's connection speed is set as 2g. And customer service agents are saying that this is the rule. And i can't use the remaining 93.69 mb data balance. This balance will be forfeited on end of validity. I can't use it.
I have mailed them, but the answer is same. What should i do?