I'm afraid we would be unable to set up a callback request; however, you're welcome to schedule a callback (if they are available) through our help centre here. You will need to enter your question, then select "contact support" at the bottom of the page in order to view the available contact methods. Callbacks are available based on volume so if you are not seeing the option appear then you can try again later or use one of the other listed support methods. You can also reach out to us on Facebook or Twitter.
To dive into your questions. Sounds like your payments have been placed on hold. Typically a prompt would appear in the admin for you to upload documents. Could you clarify if you see the prompt, or if you're having problems uploading your documents? As for your second question, could you clarify if you mean stopping your Shopify subscription when you say "halt my Shopify payments" or are you referring to something else?