Yes, you can stop paying for your account at any time. If you have already been billed for the month, you will have access to your account and analytics until the end of the month. At the time your account expires, you will lose all your data. If you restart later, you will need to pay for the data to be reinstated. If you choose to downgrade to a free plan, you are cancelling your plan and will lose data as you will be required to start and connect your accounts to a free plan.