My parents wnar me to mary a girl of their choice. They choose a girl for me but I'm receiving phone calls that this girl had several times got involved in sexual activities. How should I check that she is a virgin...

Ask her OR have her examined by a Physician.

Where are you?

First, I would want to know WHO is calling to tell you these things? Are these people trustworthy or possibly trying to ruin her reputation?

Secondly, a marriage (even arranged) should be built on trust. Try asking her and putting your trust in her before other people who may be clouding your judgement.