I called Koichi trying to sell them our dust cloth, but he didn’t want anything to do with me.
A miscellaneous cloth is a dust cloth or house cloth. It's just a cloth that you use on random things.
The reading of 雑 is different from what you've learned. Instead of ざつ it's ぞう. Just imagine using this dust cloth to wipe down a 象 (ぞう). Its trunk is particularly dusty.