What is the ruling on obtaining a credit card from an interest-based bank that is free for purchases only, with a 1% charge on the value of purchases after 55 days?

It is not permissible to deal with usurious banks at all, in order to avoid supporting them in their forbidden activities. However, if an Islamic credit card is not available and you need one, it is permissible to obtain it from a usurious bank, provided that the contract is free of any usurious conditions, such as the accrual of interest if the allowed period is exceeded.