What is this truck called?

JONNY's TOWING ROAD SERVICE TRUCK

It's a box truck.

It's largely for advertising, but it's full of tools, parts, chains, straps, lights and other things used by the company. 

Like almost ALL trucks, it serves the purpose of going from point A to point B while carrying stuff and a person or two.

A lot of towing companies buy and fit those vehicles in order to have their own "emergency response" style of vehicle to clean up after crashes, at least that's what they do with them in our area.

I don't know but i want one

It's a Ford F-550 and they use it as a roadside assistance vehicle, so the box undoubtedly is stocked with all kinds of tools and parts. And yes, it's the same box as used on Ford F-550 ambulances but adapted for a different purpose. They also adapt them for use as armored cars and police "paddy wagons". 

Box truck or box van. Very small moving companies have them and food trucks at bars or circuses. It could also hold CLOWNS.

Looks like a repurposed Ambulance made into a work truck. I've herd these are popular since the suspensions are very heavy duty 

It is a custom made and custom painted box truck on a single chassis.

Box Truck