Mavis Discount Tire

I went to the store on March 3rd, 2021. Reason - knocking noise in the rear part of suspension and worn out brakes. A 2011 Lexus ES 350 with under 80K miles.
Talked to Jefferson, who was later introduced to me as a regional manager. He allegedly diagnosed a problem, and told me, that "my mechanic recommends changing the entire suspension and all four brakes and rotors", and it will be a $2600 job. I worked in car sales for 22 years, and have some idea about how much such service may cost at a non-brand store, so we agreed on $2, 000 of which $680 was brakes, and about $1300 for new suspension. Brakes were done the same day, and parts for the rest of the job were ordered. So I came back Thursday. Jefferson told me, that it would take 2.5 to 3 hours to do the job. I waited for six hours (including a one-hour dinner break, which, I think, is simply ridiculous when customers are waiting!), and then Brian, the store manager, told me that it is ready. I drove my car about 60 yards, and, going over the first pit in the pavement, I heard a horrible, RUMBLING noise in the back of the car.
I turned back and told Brian. Ramon, the mechanic, who worked on my car said this: "Oh, it is just something in the trunk". I did not want to argue, it was 8:15 pm, and even though it was a complete idiot ism, I took stuff out of the trunk. And we tried again together with Ramon - obviously, the result was the same, a thunder like noise. Then Ramon said"ah, I know, it is a gap between a back seat and a body of your car? To change the rear struts, he had to dismantle the seats, and he did not put them back right, leaving a gap. Further, he took a soft toy (I frequently carry two little granddaughters in my car, that's why I want it to be perfect!), and he tucks that toy into that gap. Obviously, it did not change anything...
At that point my only thought was:"G-d, what have I done to my poor car!" I told Brian, the store manager, that I'd come tomorrow first thing in the morning, but I don't want to see Ramon.
Friday morning I came back, and reiterated to Brian - no Ramon. He goes:"you cannot choose the technician". Then he realized, that it is going way too far, and gave me another one, who fixed the noise and the seat. I went on the road, but the noise, that initially brought me there, still remained. I told Brian about that, the"good" technician put my car on the lift again, and found the problem. Brian wanted to charge me for the bushing, but I, being extremely upset, did not agree to pay. Brian, probably again realizing, that he is just outright wrong, ordered a part, and in about an hour's time the problem was fixed. Now, remembering Ramon, and his sloppy job, and horrible attitude, I am driving with extreme caution, not being sure, what to expect.
Summary:
1. It turned out to be, including labor, a $200 job maximum on a suspension part of my order, and I paid, with no reason, $1300, along with massive aggravation, tons of wasted time, and a lot of inconvenience. It is a huge upsell, a very unfair and unprofessional treatment of a customer!
2. I called Mavis customer service twice to file a complaint - so far no response.
3. Again, probably understanding that unfair treatment of a senior citizen, Jefferson offered a free oil change and changing a power steering fluid at no charge, but it was not a big relief, giving the circumstances of this whole story.
I am very deeply dissatisfied, and want Mavis to do something to resolve this pitiful issue.