Sec. 19. (a) The provisions of section 18 of this chapter as to rights of survivorship are determined by the form of the account at the death of a party.
(b) The form of an account may be altered by written order given by a party to the financial institution to:
(1) change the form of the account; or
(2) stop or vary payment under the terms of the account.
(c) An order or request described in subsection (b) must be:
(1) signed by a party;
(2) received by the financial institution during the party's lifetime; and
(3) not countermanded by another written order of the same party during the party's lifetime.