Plaintiff is a trading corporation and sued defendant for a balance of $50.31 on account for goods sold and delivered. The answer is a plea of payment. Issue ■was taken by reply. Defendant had judgment, and plaintiff appealed..

It is insisted by appellant that the fact that each shipment of goods' sold to defendant was accompanied by an invoice stating “pay no money to salesmen, unless they present written authority from us to collect,” distinguishes this case from the doctrine announced in Gibson v. Zeibig, 24 Mo. App. 65, to the effect that authority on the part of a salesman to collect for goods sold by him may be inferred from previous payments to him by the purchaser, acquiesced in by the principal, and for which due credit was given, and from the fact of similar payments to the agent by other dealers -with the consent of the principal. The distinction insisted upon can not be logically maintained. The written direction contained in appellant’s invoices to defendant, even if it had been assented to by the latter, did not prevent the parties making such an agreement from substituting a new one. The power to make a contract involves the power to unmake it, hence the abrogation.of the'requirement of appellant that its customers should not pay its agents without its authority in writing could be shown by any competent evidence tending to prove that appellant had waived this pre*76requisite. In the case at bar there was abundant evidence that appellant by a course of dealing with respondent had been in the habit of receiving payments of bills through the medium of the particular salesman to whom the evidence shows payment was made for those sued for in this case, and that it ratified such transactions by written acknowledgment and credit to respondent. The evidence also, shows that it pursued the same course with other dealers in the same community. The jury were therefore entitled to infer that appellant consented to this variance on the part of respondent from the directions printed in its invoices, and their verdict on that issue is conclusive on this appeal.

An examination of the instructions refused and given discloses that the rulings of the circuit court conform to the views expressed herein. Nor was there any error in the exclusion of the testimony of a witness as to the declaration of the salesman that he would not collect for his principal in the future. These declarations were hearsay as to respondent, who was not present when they were made,' and had no probative bearing whatever upon the issue as to the power of the agent to collect the bills which he had previously sold to respondent.

The judgment herein is affirmed.