Collection agency trying to collection money that I do not own from Rental Apartment. Legal help needed.?

I lived in an apartment about 23 month in CA, just shy of 2 years. According to the property owner, they send a invoice for cleaning and ect... It was never actually delivered, but "return to sender". 3 month after I moved out, I received a collection agency letter. The collection agency said that I own them 390 buck with 13 in interest and .1 USD/day. I asked for the itemized inovice, they send all the individual invoice with that "return to sender" letter without address shown. According to the contract that all charges should be pro-rated to 36 months, but collection agency does not seem to understand it and refuse to adjust the charges and keep sending the same inovice for cleaning, carpet changing..... I am happy to pay them for the money that I actually own, but collection agency do not want to make any adjustment. Should I just file a lawsuit against them and stop this non sens? Please help.