When I first came to Pakistan, all during the day I heard men walking up and down the street shouting all sorts of things. I thought it was pretty strange at first, and every time I heard someone I would ask my husband or my SIL what the man was saying. It turned out that they are like door-to-door salesman. They walk up and down the streets shouting out what ever food/service they are selling, then you come to your door and buy what you need.
There are fruit sellers, "Kayla, Seb wala!"(Banana and apple seller)-
"Timatar aur Khira, pandra rupe kilo!"(Tomato and cuccumber, 15 rupees a kilo)
This is the "Teen Dubba Wala!" -
He is like the neighborhood recycling man, he walks through the streets and you give him old newspapers, plastic bottles, old dishes, tin cans(basically anything reusable/recyclable) and he gives you a couple of Rupees by the weight of whatever you give him.