In case there is a delay in receiving SMS from M-Tala system to confirm any transaction you have carried out, contact Vodafone Customer Care Helpline at 67121.
However, there may be other reasons that may lead to you not receiving the SMS. Your SMS inbox may be full so you may have to delete some of the messages and create space for the new ones. If there is a problem with the SMS service, then you may not receive the text.