No. With Pay as you go 1, you pay for what you use. So if there are days where you don't use your phone at all, you won't pay a penny.
On the days you do use your phone, you'll pay 20p a minute, 20p a text and 20p for every 5MB of data. If your spend reaches £1 in a day, you'll unlock unlimited free minutes and texts to standard numbers, plus 500MB of data, to use until midnight.
So, if you've made a one-minute call, sent a single text message and used 5MB of data in a day, you'd pay only 60p.
Please note: you could incur some minimal data charges if any applications on your phone automatically use data. For example, if your email is set to refresh automatically every so often, or you have notifications turned on for Facebook, these 'background' actions will use data even if you're not actively using your phone.
You should be able to turn off background data in your phone's settings - see our device guides for help.