Sierra customer service can be reached by email at Customerservice@sierra.com or by live chat on the website from 5 am to 12 am (MT). The phone number is 1-800-713-4534 and can be used Monday through Friday, 7 am to 7 pm (MT) and Saturday from 8 am to 4 pm (MT). If needed, the fax number is 1-800-378-8946.