Down loading apps via App Store

Every time l try and download an app from the App Store wheat her it's free of l have to pay for it it comes up with an error message cannock download at this moment please try again later, then the app that l have treys to purchase it on my screen with waiting sitting beneath if l selected it nothing happens still says waiting, this is with my standard internet usage from provider and tyres with my wifi in my house and my moms house but still the same problem, l have tyres switching the phone on and off downloading different apps,