They can absolutely do this--they are a private company and can set the terms and conditions for anyone doing business with them (the same as your company can). For example, they can require businesses they do business with to change account numbers at any time, for any reason (e.g. they are altering their numbering system; or, as here, the company [yours] is undergoing some signficant change); and if a company is privately held, then the identity of the owner(s) has a direct and material bearing on the credit-worthiness, so changes in the credit history (or restarting the credit history) are appropriate. If you don't like how they do business, you could stop working with them and give your company's business to someone else--that's your right.