Take it back to the Repair person. Either the repair was faulty or the diagnosis was wrong and the problem was not fixed although work was done to the vehicle.
Depending on who did the repair, some Mechanics have pride in their work and do not like to be defeated by a car. Ideally you want the Repair place to be willing to complete the repair for the price you already paid.
The repair parts may have been faulty. Depending on the State you live in, some require a 30,60, or 90 Day warranty with perhaps 3000 miles. You did not say what repair was made.
Engine work for an oil leak could have been a gasket, but a warped head would either need to be milled or replaced for a new gasket to work. Valve guides can leak oil into the engine regardless of what you do to the head gasket. Likewise for oil rings on the pistons which will also be unaffected by just changing a head gasket.
You have more leverage (advantage) if the Repair facility was a Licensed garage. Complaints against the business through your State can encourage a place to fix it.
Either valve stem seals or head gasket?