My TVS — Car Service issue

I gave my Chevrolet Beat car for normal service in the month of Oct 2021 in My TVS Car service at Madurai. After the service, within a week or so, the car horn was not working properly. So I again gave it to service the horn issue. They took the car and claimed that the coil was burnt and need to change that horn coil and we need to place a request to buy that coil as we don't have new one with us and it will take a week time to get and replace it. So I took back my car and as its My TVS which is a standard and branded service center, I asked for the cost of coil for replacement and paid the full amount around Rs 3000 in advance. All these happened in Oct 2021. But when I followed up with them since Nov 1st week, they started telling that this is Diwali Time, so we have not received the courier. After a week, they started telling we have not received the courier and for sure within a week we will get and service your car. This story happened till Nov end, I was politely spoken to them understanding their reason. But later in end of Nov 2021 they told that we received the coil, give the car, we will replace it today, and I was happy to their response and gave my car to them. On the same evening, they called me and told that the coil is not fit, we have to get another coil which will take another 1 week, so we will give back the car to you and get it after a week once we received the coil. For that also, I told ok but this time make sure that you place a correct order. But after that no response from them even after several follow up. In fact, they started to ignore my calls and if I call to them thrice, once they will attend. And this story continues till Jan 2022. After that I started scolding them and after that also again they started the same story of within a week, we will replace the coil. And later by mid of Jan 2022 only I came to know that the replacement order was not done from their end. And they requested another 1 week of time to receive the coil and service the car. And again till end of Jan 2022 they were saying that the coil is not received by next week we shall close this. At last on Feb 1st 2022, they told that the coil is received and we shall replace the coil today, so I gave the car for service once again. But again on the same evening, I received a call from them saying that the coil received with some additional part as a set which costs Rs. 4800, so you have to pay additional Rs 2000. My concern is that why they order with additional part when they claimed that only the coil is the faulty. If the coil will not available without that additional part, they should have informed me when they order itself or before I paid the full amount for that coil in advance. I doubt that the person who placed the order mistakenly placed the order with the additional part and the My TVS service persons are trying to push the new coil with additional part to me and get the additional cost from my end which is not fair. Its totally their fault to place a wrong purchase order to their vendor. Totally disappointed with their performance, behavior, reply. I asked them to return back my car without changing the coil or anything as I lost the trust on them. Now to get my amount refund also they are claiming that within a week or so, it will be refunded to my account. Again not sure how long it will take from today. If I deposit this amount in normal account itself, I could have earned interest atleast Re 1 for this amount as its been more than 3 months now. Because of this issue, I faced several difficulty to drive the car without horn. In fact, for few trips I booked private cars and travelled.
Total waste of energy, time, money. From now on, I wont prefer My TVS service center to service my car.