A hold on your Thatch budget means Thatch has set aside money to cover your premium. Nothing has gone to Medicare or your insurance company yet.
You still need to make the payment. For Part C, Part D, or Medigap, pay through your insurance company's member portal with your Thatch Card. For Parts A and B, pay from your own account and then submit a reimbursement request.
The hold is just making sure the money is there when you do.