Help! Super brings a problem.

I bought a coop. When my contractor was doing my kichen, my super examed the water lines of the bathroom. The kichen is behind the bath room. He said he wanted to replace the old water lines. Since I only hired my contractor to renovate my kichen, he agrees to do it from the kichen at the time. But now, he changed his mind, and he wanna replace them in the bathroom. He said he would provide my tiles(not the original tiles) and I need to pay extra money to have my contractor fix the bathroom. Can I say no and keep the original plan I had with him? Thank you very much for your help!