regent assest management advice

is regent asset managment solutions a legit company or not?i received a call from them a few months ago with no msg...i called the number back and it was a recording saying that it was the legal department of regent asset management solutions and you could make a payment at paymentoffer.com or something like that...so i went home and looked up the site...it is a website for this company that allows you to set up a payment arrangement w/o speaking to one of there rude representatives....so i put in my phone number and it pulled a file they have for me from a us bank account that was charged off becuase it got out of control with debits and fees from some payday loan trouble that i got into...i could not pay all the money due on the account at the time so it was closed after 30 days...i received a letter several months after that from a company called Apelles...i sent them a dv letter and never received anything back....then as i said a few months ago i got the call form regent...i dignt want to be sued and i just wanted to get this debt taking care of,...so even though the amt they said i owed was significantly higher than what i though it should be...i sent up a paymnt arrangement with a pre-paod debit card becuase i did not want them having any of my bank info...i never to this day have ever received a validation letter from this company showing proof of the debt...i have now paid them approx $700 total in the last 3 months towards this debt and i wonder if i should...i have a payment of $164 that was due yesterday and i did not pay it yet because everything i have read so far soounds like a scam...but i think this company DOES sue people...and i just want to know what i should do.....should i contine to pay them and they end up probably getting more money from me then they should....or should i tell them to send me a validation letter first...or should i speak to someone at us bank....i need some advice please.