Lease agreement regarding central air conditioning?

so our lease says that we have central air conditioning. The original listing said that we had central air conditioning. When we did the walk through, we noticed two window unit air conditioners in the closet and the lady showing the house said that those were probably just supplemental for the previous tenants. We moved in the winter so we didn't test it out right away to see if it worked. When summer came around we were complaining about numerous things, ie: flooding in the basement, mold, gas leak, etc.. and we thought that since we had the window units we would just deal with it. Also we were afraid that there was something we just hadn't done that was keeping the AC from running. Like changing filters, cleaning it out, and so forth because we had a newsletter thing that came with our rent saying that we would be charged accordingly if someone was called out to do a simple task that we should have been able to do ourselves. Anyways, this summer I am pregnant in my 3rd trimester and I can NOT stand the heat. I called to get someone to come out and look at it and we were told TWICE that someone was on their way and they never showed. The third time I called, I was told that the AC didn't work, even before we moved in and the owner of the property (we rent from property managers so they don't actually own the the dwellings) refuses to replace the AC as it is too much of a cost to them. We asked if we could get the rent lowered to accommodate the change and they said that was also not an option. Our lease was 12 months and as of now it is on a month to month basis but I believe we still have to uphold to our side of the contract until we move, as do they on their part. The only option they gave us was to move to another unit that offeres central air. I am very frustrated with the whole situation because one of the criteria for moving was central air and I never had a second look at anything that didn't offer it. I never would have rented this place if I had known it only offered window units. So my question is, that since it says on our lease that we have central AC, do they have to make it work? Are they held up to their end of the contract even after our 12 months has lapsed? It was their mistake for putting central on the lease in the first place, so if the owner of the property doesn't want to pay, I believe the management company should fork up the dough to get it replaced. I'm not a very pushy or aggressive person so I hardly ever get my way. I just want to make sure that when I talk to them I have all my facts straight. Thanks, any input is greatly appreciated.