Ouch, that's a brutal stat. I've been there - it stings when you put in the effort and get silence. More often than not, the issue isn't the channel itself but the offer or the audience. Are you sending to a cold list? Or existing contacts? Because blasting 1,000 emails with zero calls screams either wrong targeting or a weak call to action.
From a retention perspective, I've found that emails work best when they're part of a sequence that nurtures trust first - not just jumping straight to the booking. Try splitting that list into segments: leads who've engaged before vs. cold contacts. For the latter, maybe lead with value (a case study, a helpful tip) before asking for the call.
Also, have you audited the subject lines? In DTC, we obsess over open rates, but for B2B it's about the preview text and the pain point you solve. If you're just saying "Book a call", that's noise. Personalise it around a specific challenge you know they face.
And honestly, if email isn't working, test SMS - but keep it under 160 characters and respect opt-in rules. Sometimes a quick text can beat a flooded inbox. But yeah, something's off. Dig into the analytics and see where the drop-off is.