Toilet Stoppage

I lived in this apartment for only 1.5 months.
One day the toilet stoppage happens. I called the manager and she called the plumber to fix it in 10 minutes.

Now the owner of the apartment want me to pay that plumer cost because in the lease it said that tenant is responsible for the cost of clogging plumbing, garbage disposal stoppage.

I don't think I should pay that cost, how to argu?
Any experience and suggestion?

I told the manager this, she also very surprised, and she didn't think I should pay that either.
also the service is "Clear Toilet Stoppage", is this different from "clogging plumbing, garbage disposal stoppage"?

Thanks for your advice.