Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.
I understand that you are unable to delete a VNET because of a SAL.
To troubleshoot this, we will need a specialized 1:1 session, where a support engineer can check the backend logs to pinpoint the issue. If you have a support plan you may file a support ticket, else please do let us know, we will try and help you get a one-time free technical support.
P.S : We will be able to provide you one-time support if and only if your subscription is not managed by a CSP
Cheers,
Kapil