I've hired a company to develop software for me. They've completed some parts of the development for me, but they've exceeded their quoted development time on another part of the project by dozens of hours and still the software doesn't work correctly. Can I cancel that part of the project and have it deducted from my bill? It's pretty obvious to me that having it completed would take a long time, if ever, and I simply don't have any more time to wait.
I would say it's an all or nothing if there aren't special provisions for each part of the programming defined in the contract.
Did you mention it in the contract, that in case project is not delivered on time , you have the right to cancel it. As the project is partially delivered the situation is tricky. May be consult a legal expert.
Would have to review the contract and which countries legal system applies to it. It may be a breach of contract or it may not.