this is how my scenario work. our customer service will use our own CRM press the CALL button to call the customer, customer service are don't know customer's phone number, have to call via our CRM. after customer service get in touch with client, customer service will request client to enter the credit card number after sound "beep" , and the client will enter the credit card number via their phone number pad, and after client enter the credit card number, the credit card number will save into our CRM system. isn't 3CX developer SDK available to do this kind of functionality? or any software available?