Do I need to pay again when moving between iPhone, Android and the web?

You do not need a second subscription to use the same Calsa account on iPhone, Android or the web. Sign in with the same account and your recognised subscription follows it. The service where you purchased still manages billing, cancellation and refunds.

A platform change does not transfer a store purchase to a different store account. Health connections also remain specific to the phone's mobile store app. If access is missing, check the Calsa sign-in method and purchase recognition before buying another subscription.