When dealing with issues with the IRS, there is an extensive variation in the amount of time it might take to get the issue resolved.
Some issues that are smaller truly can be resolved in one phone call! Simply give them a ring, explain the desired outcome, and the issue is fully resolved.
However, it is typical that issues typically take a number of months to resolve. This is especially true if the taxpayer has a variety of tax returns that need to be filed, and a variety of financial documentation that needs to be submitted.
Regardless of how long it takes to resolve the matter, it's important to put full effort forward, and work diligently to do whatever is needed to get the matter resolved.