If you are confused about Reliance GSM and Reliance Smart GSM services, this map will help you.
Note that both are now under GSM services from Reliance Communications.
Though offerings are same on both, there is a difference in APN to access GPRS.
in R-GSM APN is 'rcomnet'
in Smart APN is 'smartnet'
Check where you are and choose your APN if you are using Reliance GPRS/3G Data services.
Reliance 2G GPRS Pack - http://www.rcom.co.in/Rcom/rworld/mobilenet/plans.html