Does the appliance have a standing pilot or is it an electronic ignition?

Wow... nice! Nobody wants to take responsibility.

If you are even slightly handy, here's what you do:

Mix liquid dish soap (the kind that makes bubbles, not dishwasher detergent) in a spray bottle with some water.

You can also do this in a dish or cup and use a paint brush or basting brush.

turn on the gas and apply the soap solution to all of the pipe joints around and after the valve. Be sure to test the other end of the yellow gas line where it connects to the stove also.

if there is a gas leak in the plumbing, it will show as soap bubbles.

If not, plan on repairing / replacing the stove.

Be sure to turn off the gas valve when you are done testing.

snood's question is important to answer before any diy action. Jake's advise is sound if you are handy. Now to make sense of what you are hearing from the gas co and fitters. Normaly,the gas co tests the meter when a leak is reported. If the meter isn't leakin,they turn it off and tag it as requiring a plumber/fitter invoice for repair before service can be restored. Don't call the supplier again or your intire house will be without gas. You should call an appliance repairman. They can repair or replace anything from the red valve out including flex line. A plumber/fitter charges 300% of what the appliance man does. You could blow $150 on a plumber/fitter only to be told the problem is in the appliance and to call the appliance repair co.

klem1 is correct. Appliance person can install/repair anything past the red valve.

I was assuming from the appearance of the installation that it was new enough not to have standing pilot lights.

Of course... if you were angling for that new stove... this might be just the excuse you needed.