Your data credit is without expiration if you activate the one-time (pay-as-you-go) data. The daily and monthly plans, as the names suggest, are valid respectively for 1 and 30 days. After that, any remaining data credit will be reset, the plans will automatically renew, and new data credit will be added to your account.
You can change or cancel your plan anytime. With BNESIM, you are in control.