If your company deals with the banks in prohibited transactions, then you did well to leave this job. But you were wrong to train others on such transactions. You should have explained the Shar`i ruling. If the trainees responded positively, then praise be to Allah, and if they did not, then you have still done what is required of you.

Islamic banks are based on permissible transactions such as selling, buying, profit sharing, partnerships and other Islamically-acceptable forms of investment. The interest-based system on which commercial banks are based is a prohibited system that is based on lending and borrowing with Riba.

There is nothing wrong with you selling back to the seller the dates that he owes you in return for Dinars, on condition that it is at the current market price. There is also nothing wrong with delaying payment in full or in part, because when selling the dates for Dinars, there is no stipulation that the exchange should take place on the spot, before parting.

It is not permissible for the lender to stipulate in a loan contract that the borrower must pay back the loan with more than he took. It is permissible to make the borrower pay the costs of issuing the loan and other related services, on condition that the amount paid is equal to the real costs involved in issuing the loan.