As far as I know, the direct object of pay (when meaning provide money for something) is who or what you want to pay.
However, I read the following sentence from a (supposedly) native speaker:
Can I pay my credit card?
From the context, it is clear that the writer did not want to pay for her/his credit bank, but with it.
Another example shows the use of transitive/intransitive forms with this verb.
I guess that using the transitive form in this context is acceptable. Yet, does it sounds informal, or can it be used in every situation?
EDIT: The sentence has been (possibly hastily) written in an email.