Write a sales email for my small business. I run an online course that teaches freelancers to do their own bookkeeping.

Who it's going to: people who bought my $49 starter course in the last six months. They already know me and they've done the basics.
What I want them to do next: book a free 20-minute call about my one-on-one bookkeeping setup package.
Length: under 150 words, because most of them read email on their phones.
Brand voice: plain-spoken and friendly, no hype, no exclamation marks.
Format: plain-text email with a subject line, since it goes out through a plain-text newsletter tool.
