As long as it is interest involved, it is not permissible.

sheikh here in the uk there is a sales representative job for electronics and they are sold in a halal way with monthly instalments and deposit over a 24 or 36 month period for example but the problem is when the consumer signs the contract to buy there is normally a stipulation that if it is not paid for in this period of time then they will begin to charge interest. is this job permissible?