If you want to request a PayPal refund for a withdrawal made to Mpesa phone number using Thunes service, then the best thing to do is to reach out to Thunes via email at support@thunes.com or fill out this contact form provided by Thunes.
They do take time to reply, therefore you have to be patient.
We highly encourage people to use PayPal to Equity service as it only takes one day and you can easily reach Equity Bank in case of any problem.