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When you say your payment was 3 or 4 days late, do you mean from the billing due date?
A late payment does not become reportable to a CRA until the period of delinquency reaches 30 days.
A 30D late hurts the most for the first year -- up to 100 points. In the second year (12-24 months) it hurts for far less -- up to 40 points or so. By years 3-4 it hurts for 25-30 points. Not a big deal except for this year and a very good reminder to stay on top of your accounts (maybe use Mint or another app that aggregates all accounts?).
The best results I've found for goodwill is not to use the phone. Send a letter. Some posts on MyFico from years ago said they had luck faxing Wells Fargo with a nicely worded request.