As a parent, I thought I could rely on a company t...

As a parent, I thought I could rely on a company that supposedly provide services for children to follow the law when it comes to transportation. My son is 7 years old and extremely small for his age (in the 5th percentile on the growth chart) and has been using them to ride to and from school for 2 months now. On 2 separate occasions now, the driver has shown up without a booster seat.
I complained after the first incidence and was assured that it would not happen again, but the first time that my son had been assigned a different driver, they showed up yet again without a booster seat.
How can you ask parents/guardians to trust your services when you are putting children's lives at risk?