Slow net connet

Location/place: Vasco, Goa

Name of company/service: Vodafone

I recently purchased a Vodafone net connect 3g plan, turns out the 3g is just the logo for marketing, the speed the company is providing is very very slow . the reason for me to write the complaint is when asked what can be the problem they say its network congestion, if that the case that why sell it in the first place. Hope You understand my frustration. When i contacted the customer care al they said was that the executive or the tech team will contact and take care of the problem its already been 72hours and they did not give my docket number.
Kindly do The needful.