When selling a businees is it commercial custom that the existing contracts become the purchasers?

I am a law student and im a little confused with this situation and how to find out if something is accepted as trade/custom. Company A engaged Company B to transport its goods (term of agreement was for 4 years). 2 years later Company A sold their business to Company C. Company C refuses to use Company B's transportation services. Is there a custom that Company B's contract with Company A would transfer to Company C upon that sale? I'm basically trying to find out the rights of company B. Any help would be greatly appreciated, thanks

Normally, any commercial contract will refer to 'Company A, it's heirs and assigns". That means any contract automatically transfers to the new owner.

If that clause is not in the agreement, the question becomes whether Company C continues to operate Company A. If so, any contracts signed by A would still be enforceable.

If the 'heirs and assigns' wording is not in the contract, and Company C only buys the assets of A, not operating it as such, then B is probably out of luck.

Depends upon what you mean by: "Company A sold their business to Company C." A business consists, among other things, of assets, contract rights & contract liabilities. If Company A was itself sold than the sale included all rights & obligations, including the obligations under the contract with B. Ditto if the sale included all contract obligations (B would then be a 3d party beneficiary of the sale contract). However, if the sale included ONLY the business assets & rights (as many such sales do) then C has assumed none of A's obligations & B must look to A for any loss of profits resulting from termination of the contract.