5 Months for a settlement Letter

I was contacted in March 2015 for an account that was handed over to vertex Solutions. They called offering me a 50% discount on the account if I settled teh account. I agreed and asked for them to please email me a settlement letter, so that I could have this account paid and closed. I was then called in April, then again in June, and I have called in again and again and again, and I have had no response. I want to settle this account, but I am just not winning. I have now asked again about 1 week ago and still nothing.<br> I think these collectors prefer getting the interest money on these accounts, so they avoiding sending me a settlement. I was offered a 50% discount and now they cannot keep to their word, so they just ignoring me and not assisting me at all. what a waste of my time, airtime and effort.