Charge when using Callback and DISA

Hi all,

To understand when the use of callback and DISA via a GSM mobile network to call a landline (PSTN) via a PSTN gateway:
1 - Communication Is charged at fixed line?
2 - Is there a consumer credit line mobile phone?
In other words, is what the customer is billed GSM network, for example by calling a landline via the callback and DISA?

Thank you for your response.