It may be a big hassle, but only if you make it harder than it is.
First, STAY OFF THE PHONE!! All disputes MUST be in WRITING!! Telephone calls do not protect your rights under the law.
Send all disputes via CERTIFIED MAIL / RETURN RECIEPT REQUESTED. Be sure to put the certified # on the letter itself to prove exactly what you sent.
Keep the communications short and to the point. Dispute the item for the reason that it is not your account. DEMAND to see a signed contract. Without a signed contract, they could NOT ever win in court. Let them know that failure to remove this from collections and from your credit report WILL result in a FDCPA lawsuit. Tell them that you consider 30 days to be a "reasonable" time to get this done.
Make a demand to the credit bureaus that want to see any "validation" they get from the creditor and/or collector. They will try to get out of this, but it is your legal right. The bottom line is that they are responsible for the information THEY report on YOUR credit report. The creditor is THEIR customer and they are responsible for that relationship, not you.
On the 35th day you file the lawsuit. You file against both the credit bureaus, and the creditor and any collector involved. You are entitled to up to $1000 plus costs for FDCPA and FCRA violations. Let them know that you know this, and that you are more than willing to proceed in that direction.
Good luck.