@Cristina Zuza yes you can remove contacts after a certain period of time.its decrease your bills.you can set a rule to auto delete contacts 

How can we set this rule?

I just want to know if manually deleting contacts will reduce the cost or not?
And to switch to a lower plan, how many contacts do I need to have?

@Cristina Zuza  You can see the pricing at https://manychat.com/pricing > You have the slider to see the price per subscribers.

And yes, if you delete subscribers (manually or automatically), your billing will go down.

What do these contacts represent?
What is the risk if we delete them?

@Cristina Zuza you’ll lose all their information (tags and user fields that they have set). And they’ll need to optin again to your Manychat to become subscribers again.

Depending on the channel you’re using, you will also lose the ability to contact them (for example, for Whatsapp you can send subscribers paid messages whenever you want).

The decision on whether to delete or not is usually based on how much value a contact has for the business in the long term.

For example, if transactions happen in a short period: they become a contact, and within a week they either buy or not, and that’s it - then it doesn’t make sense to ‘collect’ subscribers.

If the buyer cycle is longer and you’re doing other marketing (Whatsapp, SMS, Email), then having contacts makes business sense.