retell vapi or elevenlabs

I'm building ai voice receptionist using Vapi and n8n, one of my prospect is using Medexa as his software to manage his calendar. There is no current api and it's a 1 way sync with google calendar. Does any of you guys have a solution on how to integrate properly my agent to complicate software like Medexa?

Hey guys, hope you’re all well. I have a problem with my AI agent — it doesn’t follow my prompt and I don’t know why. I wrote my prompt using the CLEAR method (context, limitations, examples, and rules), but it still doesn’t work as expected. If anyone has tips or a simple way to write better prompts, I’d really appreciate it. Thanks for your help!

To make Voice Agents, should I learn how to use Cal.com or solely rely on Retell Ai and n8n? If it would benefit me to use Cal.com what functions and features would I use?

I built a receptionist with n8n + Retell AI and I'm stuck on the cancel appointment workflow. It removed the appointment on Cal.com, but it didn't delete the appointment from the Google Sheets row. Appreciate your help!