Do you charge to fix software that you broke?

We're paying a company to develop an inventory system for us. I'm not familiar with normal practice, but I feel like we're being charged a lot of time to fix problems that weren't there on the previous version. At this point the system is live in production. Here is an example:

Everything works, we list some features we'd like to have. They add these features in their test environment and QA test them. Time comes to roll the update out with the new feature and it has broken 3 other previously working features. Then we end up getting charged time to fix these 3 issues. It seems this is the case with every update we have.

Is this normal?