Vodafone has introduced Flex tariff product in India. This concept originally is from its partner firms worldwide.
In India its launched in both prepaid and postpaid while globally its more of a prepaid product.
The postpaid one is same concept as Airtel MyPlan which is more of unflexible tariff than a flexible one as the name FLEX denotes for. 
We gonna talk about Vodafone Flex prepaid here which is very interesting tariff plan which actually saves you hassle of doing three different recharge for data , sms and voice.
Here on recharging for select denomination you’ll get Flex credits instead of talktime.
Details of these Flex recharges are:
MRP Rs.123
325 FLEX
Validity: 28days
MRP Rs.198
700 FLEX
Validity: 28days
MRP Rs.298
1200 FLEX
Validity: 28days
MRP Rs.396
1750 FLEX
Validity: 28days
This flex credit can be used for data, sms or voice. It’s kind of funny money concept prevalent in Australian telecom market .
Each FLEX can be used for 1MB data or 1 minute incoming roaming or 1 sms.
and 2FLEX get used for every minute of outgoing call in home or roaming circle.
So a recharge of Rs.198 gives you
either 700MB data
or 500 MB data + 100mins call
or maybe 400MB data + 100sms + 100mins calls.
Best thing is FLEX can be carry forwarded each month if recharged within validity.
Though outgoing call rate a little costly and could be improved
still it’s kind of best and innovative tariff launched by Vodafone in recent times.