a. An agreement modifying a contract subject to this chapter needs no consideration to be binding.
b. An authenticated record that precludes modification or rescission except by an authenticated record may not otherwise be modified or rescinded. In a standard form supplied by a merchant to a consumer, a term requiring an authenticated record for modification of the contract is not enforceable unless the consumer manifests assent to the term.
c. A modification of a contract and the contract as modified must satisfy the requirements of §§ 59.1-502.1 (a) and 59.1-503.7 (f) if the contract as modified is within those provisions.
d. An attempt at modification or rescission which does not satisfy subsection (b) or (c) may operate as a waiver if § 59.1-507.2 is satisfied.