How to resolve billing error without a phone call

With the frequent increases in pricing over the past few years, Simplisafe is now more expensive than my local security companies, so I didn't renew my subscription.  I got an e-mail today that said if I renewed my subscription by June 1st they would give me the next 6 months of monitoring service at half price.

I renewed and within minutes my bank account was charge for a full month's subscription price.  When I contacted support via chat, they said they weren't aware of any half price discounts and wanted me to send them a copy of the e-mail.  After reviewing it, they told me they were unable to assist me further and that I might want to try calling support for assistance.

My work schedule doesn't allow me to be on a phone call very long, and can get interrupted without notice frequently.

Does anyone know if there is an e-mail to contact customer support over a billing issue or is a phone call the only way to resolve it.