I see two charges. How can I check whether I paid twice?

Compare both transactions with your web and store receipts. Check the date, amount, plan and whether one is a message pack rather than subscription payment. Seeing two lines alone does not prove duplicate subscriptions or establish which account they belong to.

If both receipts show overlapping subscriptions for the same Calsa account, contact support. Calsa prevents duplicate web and store subscriptions. If that duplicate occurs, the web subscription is cancelled and fully refunded. Include transaction references and billing services, never full card numbers, login codes or your diary.