Actress Sneha Wagh, who plays Raj Kaur in "Sher-e-Punjab Maharaja Ranjit Singh", treated the entire unit with ice-cream as her phone suddenly rang in the middle of an important sequence.To ensure a smooth and systematic flow during shoots, the makers have come up with a rule that mobile phones must be turned off on the sets, a source said.If anyone's phone -- be it the producer, director, actor or crew -- is found ringing, as a punishment one has to pay Rs 500 penalty. When the amount is sufficient, there's a treat to all, the source added.Sneha had one such experience too."The penalty which I had to pay was Rs 500, but I decided to treat the entire unit to ice-creams."Sneha says, "A lesson learnt from the incident is now my phone is always on silent mode while we are shooting."