The surname of a limited partner shall not appear in the partnership name unless:
(1) It is also the surname of a general partner, or
(2) Prior to the time when the limited partner became such, the business has been carried on under a name in which his surname appeared.
A limited partner whose surname appears in a partnership name contrary to the provisions of the first paragraph is liable as a general partner to partnership creditors who extend credit to the partnership without actual knowledge that he is not a general partner.