First go to the website of each credit bureau. There, you can file a report to dispute items on your report. Gather all the information you can to show this is a done debt- such as conformation numbers, collection agency which you paid it off- anything to prove your case. They will review it and within a few weeks, you will hear and answer. If it is still said to be a true and valid entry, you can then call and dispute it further. This should take care of it.
Also, some companies report only so often, so it can take a while for it to fall off your credit report. Sometimes, they send in the information and then it is just never changed (lovely, isn't it?). Be sure to call Wells Fargo as well, and let them know what is going on. They will show the debt paid and will be able to submit the information needed to have it removed from your credit report.
However, if the card it still open, then it will still show on the report. If you have not already, do not close it, as limiting your line of credit can acutally hurt your credit score, as a part of it is configured using a debt to credit line ratio.
I believe it is seven years for most debt to be removed. On your credit report, it should say when it will fall off.
But you can either call or go online to file a dispute about this issue and within the next four months, if it has been paid off and is done, will fall off the negitive side of the report.
Once it is gone, your credit score will improve, but will make no significant jump. Even one bad debt can make a 700 drop to a 500 fast.
I hope this information has helped and I wish you the best of luck!
I have had the same thing happen to me, and mine was resolved through disputing the case.