Default No 3G while roaming on IDEA with ARHD

I am on ARHD 22. Having a typical problem which IDEA is not able to solve. Whenever i come to Mumbai from Gujarat I lose 3G, get only 2G in auto mode. In WCDMA mode it is not showing IDEA network at all, even though my friends are getting 3G on IDEA at same location. Tried all suggestions given by IDEA in 2 months but no solution.
Any ideas on how to resolve this issue?

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