provide me with the number you've been getting numerous of calls from

I get 2-3 calls a day from this number. I never answer it and nobody ever leaves a message.  I have been scammed by calls like this. DO NOT GIVE THEM ANY INFORMATION. If they say you can only pay with a Green Dot Money Pack card. It is a scam. If a message is left on vmail, the number they urgently need you to call is never the number they call from.

randomly calling daily who is this

Like Jim said, tell then you never received the letter.

This is a DEBT COLLECTION agency and you reset the clock if you say you get the letter or answer any question.

A LOT of the debts they are trying to collect are "zombie" debts.  Also be careful if you filed a bankruptcy, or are in process of one.  Don't say anything other than "This debt is in a bankruptcy proceeding."  Give them your attorney name and case number and nothing else.  If you are in process this will also stop the calls by law.  If they call in violation ask your attorney about sanctions against them.

If the debt was discharged in a prior bankruptcy advise them of that, give them the attorney name and case number.

Do not talk to them or let them bullcrap you.  A recent ploy is to offer to settle for a lot less than you owe and to "clear your credit record."  Don't do it - you could be reaffirming the debt and end up having to pay something that was discharged.  I get 2 - 3 calls a month and a letter from a debt that was discharged in bankruptcy 10 years ago.  I just trash it, block their current number and move on.

Some agencies are using prepaid cell phones.  They get them from WalMart, convenience stores and so forth.  These "burner" phones are cheap and easily replaceable.

Also be vary of overseas debt collectors.  Not being familiar with US law, they will say things like "pay or we will have a warrant issued for your arrest" or other bogus info.

DO NOT ADMIT ANYTHING TO THE DEBT COLLECTION COMPANY.
DO NOT GIVE THEM ANY INFORMATION.
DO NOT SPEAK WITH THEM.
You HAVE TO Tell them you HAVE NOT RECEIVED ANY LETTER,
The reason for this is that, if you admit to receiving the letter, then the clock has started for your 30 day response to the DEBT. If they don't hear from you within 30 days, then the debt is considered valid by the Fair Credit Reporting Act or something like that. This means you will likely have to repay the debt or hire an attorney.

You can ask them to send another letter of confirmation by mail, and to Please also put in any quesions they might have for you so you can reply by mail.
GOOD LUCK
Jim

CORRECTION TO BELOW ADVICE.
You HAVE TO Tell them you HAVE NOT RECEIVED THE LETTER, The reason for this is that, if you admit to receiving the letter, then the clock has started for your 30 day response to the DEBT. If they don't hear from you within 30 days, then the debt is considered valid by the Fair Credit Reporting Act or something like that. This means you will likely have to repay the debt or hire an attorney.

You can ask them to send another letter of confirmation by mail, and to Please also put in any quesions they might have for you so you can reply by mail.
GOOD LUCK
Jim

Says he wants the last four of your social security to confirm it's you. DON'T GIVE IT TO THEM. They say they have a personal business matter they need to discuss with you and that they have sent a letter to your home address, and ask if you have received it. they probably have sent nothing, as is the usual standard, but claim they do mail out letters. In any case do yourself a favor and tell them that you prefer to do all correspondence by mail. And that you can not give them the last four of your social security for protection. They will claim that no one can do anything with your last four social security numbers, but they are lying to you, as if someone has a lot of your other info, like date of birth, full name, name of your mother's maiden name, your address, and all they need then to confirm that they are you is something like the last four digits of your social security number.
TELL THEM YOU PREFER TO CORRESPOND BY MAIL. TELL THEM THAT YOU HAVE RECIEVED THEIR LETTER AND TO FORWARD ANOTHER LETTER FOR CONFIRMATION AND TO ASK ANY QUESTIONS IN THE LETTER SO YOU CAN RESPOND IN WRITING. THEY ARE NOT ALLOWED TO ASK CERTAIN QUESTIONS, SO THIS LIMITS WHAT THEY CAN GET ON YOU.
Good Luck

Its a debt collector that collects on bills that are old and way past the statute of limitations.

FRA debt collector