Normally, I correct pieces of writing by simply amending the original in red. However, there are so many errors of grammar, construction, word order, and incomprehensible sections that it is impossible to do that. I think I understand what happened. Here is my attempt based on what I think happened:
Originally Posted by meela
"Recently, your cashier Mr Taj received Rs.7000 from Rais (our member of staff) as payment for 6 telephone bills for the month of August 2012. As he was very busy, Rais did not count the number of telephone bills marked as paid before he left the counter. However, when Rais returned to our office he found that he only had 5 telephone bills marked as paid, instead of 6. When we received our September telephone bill it showed an outstanding amount of Rs.3500. We can only assume that your cashier Mr Taj accidentally kept Rs.3500 and did not count it as payment of the sixth telephone bill."
If I'm right, you are basically saying that Mr Rais kept Rs.3500, accidentally or otherwise.
Remember - correct capitalisation, punctuation and spacing make posts much easier to read.