Suddenly surprised by 3 small charges under $40 fr...

Suddenly surprised by 3 small charges under $40 from a few years ago, showing up as Collections on my credit report. Didn't have any old unpaid bills from them, and they never contacted me via mail or phone. So, after researching, I got in touch with Ladonna/Zotec Partners(they do their billing now). She stated if I paid it, she can get it off of my credit quickly, which she did.
Before I paid it, I searched thru my old checkbook, and didn't see where I had paid that amount total or 3 small, so maybe it was valid....I've just been rebuilding my credit and 3 collections knocked it down, I wanted it gone.
She did mention I had one other one they billed wrong as well a few years ago, but they weren't going to hit my credit because they had sent to the wrong insurance. That is probably what happened with these charges, but they NEVER let me know, and never asked to verify...
They were able to send me the itemized bill in the mail where I was charged(they break up the charges so it hits credit worse with multiple collections instead of just 1). I paid it as soon as I had that, but I still don't think they should have just let it go to collections without even 1 bill over the past few years.