Mobile phone operators can apply the "reasonable use policy" to ensure that all customers have access and can benefit from the rules of "roaming like at home" (roaming services with national tariff, without surcharges) when travelling within the EU.
This limitation means that your operator can apply fair, reasonable, and proportionate control mechanisms to avoid the abusive use of these rules.
When roaming, there is no volume restriction for voice calls and text messages (SMS). Calls or messages not included in your contract will be subject to the same rates as your country of origin.
However, rules and limits apply to the volume of data billed at national prices. The data limits depend on the type of contract.
In some specific cases (see below), you may have to pay a data roaming surcharge equal to the maximum cap for EU wholesale data rates (€ 3 / GB of data in 2021, plus VAT).