(a) Except as provided by Subsection (b), if a person has contracted in writing to perform an obligation in a particular county, expressly naming the county or a definite place in that county by that writing, suit on or by reason of the obligation may be brought against him either in that county or in the county in which the defendant has his domicile.
(b) In an action founded on a contractual obligation of the defendant to pay money arising out of or based on a consumer transaction for goods, services, loans, or extensions of credit intended primarily for personal, family, household, or agricultural use, suit by a creditor on or by reason of the obligation may be brought against the defendant either in the county in which the defendant in fact signed the contract or in the county in which the defendant resides when the action is commenced. No term or statement contained in an obligation described in this section shall constitute a waiver of these provisions.