Grey Stone Alliance is formly Elite Recovery.
Overall.... They can call before sending a letter. They are probably calling to verify the address is correct. They have 3 days to mail out the letter of representation, also known as a dunning letter, to give you a 30 day window to dispute the bill owed. It does not matter at what point in the conversation the mini-miranda (informing you that he is a debt collector and any information obtained will be used for that purpose).
Collection agencies are really easy to deal with. If you can find the proof that you paid it, send it to them. Ask what day the last time the bill was paid. That will give you a general direction of where to look.
Also, if you find it on your credit report before they spoke with you, that IS NOT necessarily a violation. They usually give you anywhere from 30-60 days to either dispute that debt or to take care of it prior to it being reported.
ALSO, something that people don't understand is.... although you may have an account that was opened in 1999, it would be 10 years old. BUT the statute of limitations is in effect 7 years from the date of last activity, meaning the last day the account was paid on. So if the last time you paid the account was any time after 2002, it will appear on you credit report. HOWEVER, for people who are interested in cleaning up their credit and can not afford to pay the whole thing at once, but would like to at some point.... well here is a good tip for you. Take a SETTLEMENT. This will stop the interest from accruing on the account and it looks much better than not paying it at all. Then when you have the money to pay the rest of it, you won't have any interest that has accrued since your last payment.
Collection agencies are really not that bad. You'll come across some people that are very rude and will be condescending, but that is when you turn to that collector and say.... "I'm helping you hit your quota by talking to you... you may want to change your tone and be a bit less evasive. This way we can help each other."