problems with rental contract

[Maartenvdw]

Hello,

I just moved to Austria (for the 2th time) for 3 months and have a question.
Halfway of September I contacted a company to rent an room in a student WG from them.
I forgot to mention my stay in the room.

When I received the contract by mail I saw that the date was for almost 1 year. I changed the dates on the contract by strikethrough the end date and placed my end date underneeth.
After that I sent the contract back to the company. I got the reaction back from them that it is not possible to change the contract and they asked me to sign the contract again without any change.
My reactie on that was that I wanted a contract for just 3 months. He sayd that he had to ask his boss about that.

I had to wait for a really long time for any answer, even after asking for it.
In the mean time I had to start my internship already without any knowlage about if it was possible to rent it for this period or not. Someone I know also lived there and got already my key, even though I did not know anything about my new contract.

I did unfortunately I did not find something else in the mean time. Because I had no place to stay I decided to stay there as long as I did not find anything else. When I was there I passed by 2 times at there office to ask them whats up with my new contract. They still had to talk with there boss. In the mean time we are more than 20 days furether.
After 1 week living there I decided to move out and not wait for a new contract and I give the keys back.

Now, they send me a mail that I have to pay for the whole semster. The contract they first did not accept because of the date-change I made are they now using to let me pay for the whole semester.

Is that legally possible?

Thanks!
Maarten