My invoices take place on the 19th of each month. I would like to change my subscription for the following month, from March 19th to April 19th. If I want to change my subscription for that period, when should I do it? Before the 19th of March, on the 19th of March itself, or after? I am afraid that if I change it today, I will be charged for this new subscription in this month's bill. I hope you can help me!