Basically I have a BMW 4 series that recently broke down. I had it towed to the mechanics were they were happy to work on it, just for clarification the issue is that whenever I attempt to start the car it fails, I left my car with and came back a couple days later to find they had replaced my alternator, the car was turned on when I arrived and I took it home once I turned it off I found it still had the same issue It wouldn’t start I had already paid and was told that it was an issue with my battery losing charge after driving, before I got home I drove it for 30 minutes, I phoned back were they claimed my battery must’ve completely gone flat I got my battery and new alternator test and found that both where completely fine yet the problem persisted, after bringing my car back to the mechanics they are now claiming it to me an issue with my starter ignition, which leads me to think why have I paid for a new alternator when questioned on this the mechanics claimed it was also broken, which I do not believe and makes me unwilling to pay anymore, my car has a start stop ignition and I’m unsure how to advance with this if it is my ignition that is the problem I can’t see why my alternator was concluded to be the issue when I paid for them to take time to find the issue any ideas ?