No, not unless you have an agreed arrangement due to the type of therapy you are engaging in. Therapists need to be focused on the clients they have that day.
It’s also not always helpful for you as a client to have constant access to your therapist. Often the time between sessions is a useful and necessary space to reflect on what came up for you during your sessions.
If you need to contact your therapist regarding a change to your upcoming session, your therapist's email address can be found in your session confirmation emails, or by clicking on the therapist's name in your Client Dashboard.