I've called every 6 months to get a limit increase on my Wells Fargo Visa, and each time my score went up slightly. They just ask for your annual income, and approve you over the phone without an inquiry into your report. On the other hand, I called my Chase MasterCard to get a limit increase and they required me to authorize an credit check. I authorized the check, got the increase, but my FICO went down due to the inquiry.