Weed Man

I was approached by a telemarketer a few months ago about how WeedMan would do wonders for my lawn and how i would not have to pay for the service if I was not satisfied. So here I am months after agreeing to allow them to 'fix' my lawn realizing my huge mistake. I thought my grass could use help before, well now - my grass is essentially dead....in large patches; except for the weeds - they seem to be doing exceptionally well. The last straw was the recent fertilizer treatment (as I had called to say the lawn was covered with weeds); a few days after the fertilizer, I noticed brown burned patches all over my grass. I can't say it was due to sunny/dry weather, as its been overcast/rainy for weeks and comparing my lawn to my neighbours....omg - it looks awful - so I have to assume it was a direct result of the fertilizer they applied. I called them to complain again and they said the grass was dead because of thatch. uh huh. They also said that for an additional $90 they could dethatch my lawn and that would 'fix' it. I told them I was cancelling my service, I was dissatisfied with the results and that I am not going to pay for the last treatment (I should actually be asking for a full refund $350 paid so far). They said I HAD to pay for the last treatment and so began the argument back and forth....'I'm not paying you another cent' - 'oh yes you are" Who is this company - they are awful! Do not, under any circumstances let them near your lawn. I'm not quite sure of my recourse here, any suggestions?