Here’s what can happen: Your credit score is determined in part by the difference between the credit limit on your cards and the balances you carry (also known as “credit utilization”). Virtually all credit card issuers report your credit limit to the credit bureaus, and this is used in the calculation of your score.

The problem is that a no-limit credit card company has to report some value as the “limit” to the credit reporting companies. If card issuer reports an arbitrary limit that happens to be low while also reporting what you spend (and you spend a lot), you could seeing a lower credit score because of it. The difference between your credit limit and the “balance” could be very small (which is bad for your credit score).

Many consumer advocates believe that the best thing for the no-limit card issuers to report is your highest-ever balance as your actual credit limit. Unfortunately, it seems like this doesn’t always happen, and the unsuspecting consumer may have a lower credit score than might otherwise seem fair.

The only thing you can do is get your credit report and see what the card issuer is reporting. If it looks like they’re doing this to you, call customer service to complain.