MAJOR car service actually just a minor part replacement

On 2 June 2021 I took my car in for a supposedly MAJOR service. Since then my car hasn't been the same. Suddenly there were minor oil leaks and on 21 July 2021 when I got home my dad showed me the big oil leak where my car usually stands at night. When we jacked it up, we found oil leaks on two places. The one leak coming from the samp. Apparently their MAJOR car service doesn't entail jacking a car up to check underneath the car for any oil leaks or problems. Now it is going to cost me more to have their half-done-work sorted out. Money I don't have! Their MAJOR service was actually a minor part replacement.