Speakers not working after repair, MacBook detects earphones in jack

The keyboard on a family member’s Macbook Pro (13”, late 2016, Function Keys) broke. Since it was covered under the repair program, we took it to an Apple Authorized Service Provider (not Apple themselves) so that it could be fixed for free.

The repair took a few days, and we received the Macbook back. The keyboard now behaves normally. Unfortunately, the speakers (which were perfectly fine before the repair) no longer work. In settings, it seems that the Mac is detecting an earphone in the headphone jack, and so the speakers are not emitting any sound. Upon inserting earphones, the sound coming out of them is extremely muffled, and noisy. Even after removing the earphones from the jack, the laptop is still detecting something in the jack, and so does not emit sound through the speakers.

We took the Macbook back to the repair shop on the following weekend. The technician blamed us for the fault, and said that replacing the keyboard had nothing to do with the speakers, so there is no chance he could have done anything to ruin them. He took the laptop in, telling us it was up to his manager whether or not we would be charged for the sound to be repaired. He would contact us when a decision is made, and we could then choose to either proceed with the repair, or take the laptop somewhere else. We await his response right now.

In the meantime I had a couple of questions:

1- Since the entirety of the Macbook’s keyboard was not working, I read that technicians fix the laptop by replacing the whole of the upper case. Does the upper case include the speakers/ earphone jack? Perhaps the technician replaced our upper case with one containing faulty components.

2- If he charges us for the repair, what steps can we take against this individual. If we file a complaint against this repair shop with Apple, what will we be expected to present as evidence for our case?