Process server calling

Today I received four calls in a row at work from 000-000-0000. As I received those calls, a friend texted me to tell me that someone called him from this same number and said they were a process server looking for me with a summons and that if I did not respond to it, they were going to issue a warrant, which I know they can't do. Then, later in the day a family member texted me and said she had received a message on her home machine for me with the same information as above and that papers were being filed at the county clerk's office. A phone number of 888-712-3109 was left along with a reference number. At this point, I was frustrated so I called the number back and asked what business it was. I was told it was Bertrand Management Group. I gave him the reference number and he told me they were a law office working for a third party and that they could give me a settlement offer before it went to court. He said they usually tried to contact people first to avoid court. I told him I would need some proof of this debt and he said since it was a new account to them, they would not have statements or anything on it until mid-November. I still told him that I wanted some sort of proof that this was my account and if I should just wait to be issued a summons. He then said he could email me a purchase agreement because if it went to court, the attorneys would produce receipts with my signature to prove that it was me and that was a lot of work. After getting off the phone with him, I checked with my local civil court and of course, nothing had been filed. I never received any kind of collections notice from this company. He has since emailed me a settlement offer. Can I dispute the debt off the settlement letter? I never once told him this was my debt and made several statements that I would need some proof that it was my debt.