There is no wrong in
selling a commodity by credit sale at a higher price than the cash price; however, the price must be specified in the beginning and the time span should also be specified when concluding the contract. If the company specifies different schemes for payment in a single transaction, and none of these payment schemes is chosen when concluding the contract, the transaction is invalid because the time span is not specified in the contract. Moreover, it is similar to Riba (usury) of the Pre-Islamic period because people at this time used to increase the rate of interest if the purchaser failed to pay the first payment.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.