Have you tracked the totals and made note of when it would end? Have you asked HR or the Judgment Creditor? Start there. Do everything in writing if you can so you have a paper trail. Obviously HR can be done by phone or in person, but keep a record of what you are told, and ask for verification of these changes.
I would have to see the pay stubs to try to figure out why the garnishment increased, and even that may not explain it on its own. Just so you're aware, a bankruptcy case can end most garnishments (all types should stop at least temporarily). You should see an attorney to see if they can help get the garnishment stopped altogether.
Nothing contained in this message should be construed as legal advice.
Wage garnishment is calculated on a percentage of net take-home wages (after taxes) above the Federal Minimum Wage on a 30-hour work week. Did your net wages increase recently? My legal guide on Avvo explains in detail how to lower this amount to make the amount bearable and fair, as well as suggesting other options to bearing this for years, which is costing you money, as the judgment accrues interest and the costs of the Sheriff and other costs are passed on to you.
I blogged about almost this exact same situation as you described and my thoughts on what could be done about it. The link to that blog is the second link, below.
If you contact my office for a free consultation, please mention this posting on Avvo.
Robert Stempler (please see DISCLAIMER below)
NOTICE: The above statements are provided for general information purposes only and are not intended as legal advice or advice of any sort for a specific case or legal matter. If you do not have a signed attorney-client fee agreement with the Consumer Law Office of Robert Stempler, APC ("the Firm"), then until such written fee agreement is provided and signed by both a prospective client and attorney for a particular case, neither Mr. Stempler nor the Firm will represent you nor will they be your attorney in any matter and you remain responsible for retaining your own attorney and for compliance with any and all deadlines and for any statutes of limitations that may pertain to potential claims. Comments made on a public forum, such as Avvo.com, to not have any confidentiality because others may read them. If you desire a private consultation with Mr. Stempler that is confidential, please go to www.StopCollectionLawsuits.com and submit a free eCase Review. The result portrayed for a client was dependent on the facts of that case. Results will differ if based on different facts. The Firm and Mr. Stempler are a debt relief agency. The Firm and Mr. Stempler help people file for bankruptcy relief under the Bankruptcy Code.