Manju agarwal maid services
Asking for monies not due to them

I had registered with the agency in September. They sent me a maid to look after my kids. However 6 months later the said maid had to quit on account of personal reasons. when I called them for a replacement they mentioned that a replacement is given only within 6 months. since the maid left after 6 months they could not help me. I did not pursue the matter since i was not too sure of what agreement i signed with them in the beginning. In the meanwhile i employed some other maid, however they were not up to the mark. After around 4 months the maid that was sent by them contacted me directly and mentioned that she was in need of a job and if i could take her part time it would suit her well. Since I had no other maid i re-employed this maid - however this time the agency was no where in the picture. In Sept - the agency called the maid to check where she was working and she mentioned that since they could not place her suitably she contacted me directly and was working on different terms wth me. right away the agency sends me a bill for yearly service charges - when i called to enquire why i was being charged this amount - they said that since the maid was with me for a year they are charging me the amount. I explained the facts and also reminded them that they had not sent me a replacement. They send me a letter from a lawyer threatening to sue me if i did not pay the fee. they also mentioned that i was cheating them by keeping the maid for over a year and still lying to them. When i mentioned this to my maid she was surprised they could say something like this because she said that they were aware of the fact that she was not working with me because they had given her alternate employement which she was not satisfied with. I sent them this response through a lawyer - however they are still harassing me with more letters from their lawyer now asking for the initial fee stating that i had not even paid them that which is a blatant lie. Please let me know what legal recourse I can take to stop such harrassment.