Cost control is one of the main ideas behind the NAKED mobile service. Instead of charging a fixed amount regardless of usage, the monthly cost starts at €0 and increases according to actual consumption. NAKED also says that customers receive a notification before they move into a higher spending zone. This gives users an opportunity to monitor how their usage is affecting the monthly bill. The website includes a tariff calculator that can be used to estimate expenses based on internet data and calls/SMS. More information about this approach is available at https://naked.net/. The service also describes itself as providing greater control over mobile spending and avoiding fixed payments for unused services. Another listed feature is no usage, no charges, meaning that customers are not charged for mobile usage they did not make. The pricing information shown on the page includes several spending levels, with the highest displayed amount being €27.99. This approach may be useful for people whose mobile habits vary significantly between months. Rather than selecting a large package in advance, users can monitor actual consumption and pay according to the services they use.