Occasionally the telephone company makes a special offer on phone top-up cards, the way most of the population pays for their phone calls. 25,000 cfa (£25) will get you 37,500 cfa, 10,000 cfa will get you 15,000 cfa and so on. I walked along the streets quiet after Friday prayer, and saw a young guy flapping the orange cards in the way of passing pedestrians.

"Do you have 25,000?" I asked him.
"I have 10,000, and 5,000" he said.
"OK, but I want 25,000, so, thanks," I said and tried to walk away.
"But I have 10,000," the guy said, a little agressively. "It's the same thing."
"But it's not the same thing. Sorry."
"Buy 10,000," he almost shouted at me.

I tried the next guy.

"I have 5,000 and 5,000 and 5,000 and 5,000 and 5,000. It's the same thing."

I could not argue with him.