Text messaging system to work with booking system

I have a website built in php/mysql. It is a booking and reporting system. My client has very little money left but he is looking for a text messaging system to send a text to the customer when said customer books through the website. Then another text should be sent when it is close to the time they booked to tell them what time they are due for their booking to be available. A total of 3 - 4 text should be sent for this system. Please send bid and examples of your work or any previous work you've done similar to this.