(g) Upon any offer, agreement, representation, assurance, understanding, commitment, or contract of a bank, savings and loan association, or credit union, to extend credit or to make a loan in excess of fifty thousand dollars, primarily for nonagricultural, business or commercial purposes, not including charge or credit card accounts, personal lines of credit, overdrafts, or any other consumer account: Provided, That this subsection shall not apply to any offer, agreement, representation, assurance, understanding, commitment or contract with a bank, savings and loan association or credit union in which a transaction has been completed as evidenced by a fund transfer; Unless the offer, promise, contract, agreement, representation, assurance, or ratification, or some memorandum or note thereof, be in writing and signed by the party to be charged thereby or his agent. But the consideration need not be set forth or expressed in the writing; and it may be proved (where a consideration is necessary) by other evidence.