Exam Booking Cancelled Even Though I Paid in Full!!!

Moonstone has disabled my account, effectively blocking me from making any further exam booking under my profile. Additionally, on the 20th of December they were not answering their phones more than 30 minutes the EARLY YEAR-END CLOSING TIME they themselves set for themselves. So as a result I promptly set up another profile, made a booking for 04th February 2024, paid using the correct invoice number and emailed the proof of payment, yet this morning again they "temporarily" cancelled my booking due to "non-payment"???