BOWMAN,HIENTZ,BOSCIA&VICIAN Trying to collect on debt which is also being billed by another collector. Amount owed may be greater. Merrillville, Indiana

I received a letter from this company regarding a debt currently being billed by another co. Midland Funding. This letter was not notification of legal action but a request for payment on the same debt. Midland Finance acquired the debt from Chase after I stopped payment to Chase because of unwarrented monthly rises in interest.  I had exellent credit, had always paid on time, never missed a payment or gone over limit. Chase abitrarilly began raising the interest to the point I could no longer make the min. payments.  The account was then acquired by Midland with whom I refused any correspondence. So now this account seems to also be in the hands of the supposed law firm named above.  The letter I have seems to be similar to ones I've read about on this site, it even has a detachable billing statement to return with payment. I have never been in any financial situation like this and am unsure how to proceed. I am going to ask for verification from them as to what contractual aggreement they feel they have to collect directly from me.  The letter states that the amount noted may grow by the time I make payment, and so I may actually owe more.  Can two companies try to collect on the same debt ?