not refunding vodafone 3g data pack but as per plan they have to refund

Location/place: DELHI

Name of company/service: VODAFONE

Dear Sir,
On 8july2012 ,i have purchase the vodafone 3g data pack (prepaid). The plan was that if you are not satisfy with the service ,you can return within 15 days and will get refund the same ammount. but now no one giving response and taking responsibility for this case. on-line vodafone costumer care said that pls visit vodafone store ,vodafone store executives is telling this is not in our hand the engineer team will come to your address within 2 days and they will take action.
Please helh me to get the refund of my money.

THANKS AND REGARDS,
JAI SINGH