Mechanic did not fix car

I drove in my vehicle to service at BMW dealership because engine light was
on and running at low speed its a 2012 BMW X5
they told me it have lots of codes come up but the main one is the high
pressure fuel pump and cost $3000 to repair , i agreed to have it repaired
two days later they told me they took it out for the 2nd test drive and it stalled
on the highway, they towed it back to the dealership and told me its a major
engine issue and cannot fix it. what are my rights they told me I have to get
my vehicle towed out and they will try to remove the part??? what should I
do??