There is nothing wrong with using credit cards if they are free of things that are forbidden by sharee’ah, which are as follows:
1 – Stipulating that a penalty or extra amount must be paid if there is any delay in payment.
2 – Taking more than the actual costs in return for withdrawal of money.
The Fiqh Council issued a statement no. 108 (1/12) concerning uncovered credit cards and the ruling on the fees charged by the bank. There follows the text of the statement:
With reference to the Council’s statement during its tenth conference no. 102/4/10, on the topic of uncovered credit cards. After listening to the discussions on this topic between fuqaha’ and economists, and referring to the definition of credit cards in its statement no. 63/1/7, which defined an uncovered credit card as “a document given by the issuer (the issuing bank) to a person or entity (the cardholder) on the basis of a contract which enables the cardholder to purchase goods or services from anyone who accepts this document (the business) without paying money straight away because the issuer is committed to paying and payment is made from the issuer’s account; the issuer then charges the cardholder who is obliged to pay by a certain deadline. Some of them impose interest or riba on the entire unpaid balance after a specified length of time from the date of billing, and some do not impose interest. The Council has determined the following:
Firstly: It is not permissible to issue non-covered credit cards or to use them, if it is stipulated that riba or interest be paid, even if the one who requests the card is determined to pay it off within the free grace period.
Secondly: It is permissible to issue non-covered credit cards so long as they do not include conditions stipulating that riba or interest be paid on the debt.
From that we have deduced the following:
(a) It is permissible for the issuer to charge the cardholder set fees when issuing or renewing the card, on the basis of the real cost of the services offered.
(b) It is permissible for the issuing bank to take commission from the business on the cardholder’s purchases, so long as the business sells it for the same price as transactions for cash.
Thirdly: Cash withdrawals made by the cardholder are a loan from the issuer. There is nothing Islamically wrong with that so long as it does not lead to interest charges and the set fees are not regarded as interest which has nothing to do with the amount of the loan or the length of the loan period. Anything more than the actual cost of services is haraam because it is riba which is forbidden in sharee’ah, as was stated by the Council in its resolution no. 13 (10/2) and 13 (1/3).
Fourthly: It is not permissible to buy gold and silver or currencies with the uncovered credit card. End quote.
See also the answer to question no. 13725 for information on the prohibition on using the “Samba Visa” credit card even if it is paid off within the stipulated time period.
If the credit card is of a permissible type that is free of haraam matters, then there is nothing wrong with you working to market it. But if it is of the haraam type, then it is not permissible for you to work in this job, because that is helping in sin and transgression. Allaah says (interpretation of the meaning):
“Help you one another in Al‑Birr and At‑Taqwa (virtue, righteousness and piety); but do not help one another in sin and transgression. And fear Allaah. Verily, Allaah is Severe in punishment”
And the Messenger of Allaah (peace and blessings of Allaah be upon him) cursed those who record and witness riba, as Muslim (1598) narrated from Jaabir (may Allaah be pleased with him) who said: The Messenger of Allaah (peace and blessings of Allaah be upon him) cursed the one who consumes riba and the one who pays it, the one who writes it down and the two who witness it, and he said: they are all the same.
And Allaah knows best.