ACCOUNT CONTROL TECHNOLOGY This 3rd party debt collector agency arranged to have my payroll check garnished without my permission, without my having to sign anything, never producing any documents that establish that I have ent Canoga Park, California

Technically when you first took out the student loan you signed what they call a prommisory note, in that note it said that if for any reason at all you didn't pay on your student loan and went into a default status that you are subject to garnishments, tax offsets..etc...THIS IS A "FEDERAL LOAN". Meaning that it's not just going to go away, it will follow you and your credit report around until you finally pay it. That's right, not even bankruptcy.

It also states in that note that if you ever move, or change your phone number you would contact your original lender and update with them. did you do that everytime??? I doubt it. YOU do not have to agree with the moving your loan around, that is a consequence of YOU not paying on your student loan.

Once the Client approves your loan for garnishment they send a letter to the address they had on file. Basically meaning if they have a addy that has no mail return they have to assume that it is yours.

For what ever reason you didnt pay on your student loan, it is not other peoples fault that you went into default and now are having to deal with it, but them garnishing you is not illegal. You can get that garnishment stopped however if you join in a payment program with them.

They do not need a contract to garnish your wages or take your income tax.  If you have a defaulted federal student loan, all they need is the name of your employer, address and phone number.  They do not need to have your permission or consent to do this.  It is definitely not illegal for them to do this.  Whether it was this collection agency or a different agency they would still garnish your wages and take your income tax.  

In fact, it is not the collection agency who approves this, it is who you got your student loan from.  You are not paying this collection agency, you are paying the client. There is only one reason it is at a collection agency, its fallen into default because of failure to pay by the borrower.  Unless you live in the state of Pennsylvania, you can and almost definitely will be garnished and have your income tax taken.  

Please call a local non Profit No Charge debt advisory person in your state.

Your local state government will be happy to provide a list.

This is important because depending on where you live you are mistaken on at least one of the points you made and it will harm you for a long long time to come.