Legal Question in Consumer Law in Virginia

Possibly, if you order their services knowing that there is a cost for the services, you are agreeing to pay for the services.

This is like going to a restaurant. You see the prices on the menu. Then you say "I will have the lasagne." You know what the price is because it says it there on the menu.

You don't sign a contract at the restaurant. You don't even promise to pay. But it is implied

For the exterminating company to prove their case, they must prove that you ASKED for the services (and of course they have to prove that they actually also DID the work, of course).

For them to prove the dollar amount of the services that they can get paid for, they would either have to prove (a) you SAW the prices that they normally charge and that by responding to the posted prices you agreed with them, or (b) they would have to prove the prevailing prices for those services that are normal in order to prove the "fair market value" of the services to decide on the amount that you owe them.