Which is the lawful profession: that of a credit card sales representative in a bank, or a sales representative in an insurance company?

It is not permissible to work in selling prohibited credit cards (usurious or those involving gharar (definition)/excessive uncertainty), but it is permissible to sell permissible ones. As for working in insurance companies, it is permissible if it is cooperative insurance, and impermissible if it is commercial. One must avoid prohibited work except in cases of extreme necessity. Whoever fears Allah, is patient, and relies upon Him, Allah will provide for them from sources they never anticipated.