Trying to explain the difference between ‘Pay as you go’ and ‘Contract’

I was sorting out a mobile phone contract at the weekend, and while I was waiting for the stone-age technology in Carphone Warehouse was doing its thing, I was left alone while the member of staff left to deal with another customer. The upshot of a very long conversation (don’t worry the computer was still chugging away) was the member of staff trying to explain the difference between ‘contract’ and ‘pay-as-you-go’ – without much success. To fill the time I started trying in my head, and then on to paper (well, on to screen). Here’s where I ended up:

Contract
You pay for a fixed number of minutes and texts every month. If you use more, you pay for them on your bill at the end of the month.

Pay-as-you-go
You buy minutes and texts when you need them. When you need more you have to buy them.