Poor "Major" service

Absolutely Ridiculous service. My car was in for a "major" service in Jan 2023. When I collected my vehicle from them, my speedometer didn't work after they worked on the vehicle, I then returned and they reconnected it, ever since my vehicle surges and jerking at high speed with very worsen fuel economy. Before I took it in for its "major" service my vehicle has never had these symptom's or were poor on fuel economy. I took it back on Thursday 13 Apr 2023 and they claim it "could be" the coil pack or bougi cord set. When I confronted them and asked why this was never inspected during a major service they claimed that this forms part of electrical components and that nothing in this regard was noticed. In my view when you perform a major service then every little spec on the vehicle should be tested and diagnosed which in this fact isn't happening. I would not recommend anyone to service or have you vehicle repaired through them, they all just about making a quick buck.