How can I cancel my scheduled repayment so I can go ahead and pay it now?

TO CANCEL A TAX PAYMENT YOU SCHEDULED

If your return was accepted, you cannot change your payment method  or payment date.  The only thing you can do is cancel the payment and then pay by a different method on your own.

• Call IRS e-file Payment Services 24/7 at 1-888-353-4537 to ask about or cancel your payment, but please wait 7 to 10 days after your return was accepted before calling.
• Cancellation requests must be received no later than 11:59 p.m. ET two business days prior to the scheduled payment date.

 If you have federal tax due you can pay by mailing your payment with the 1040V voucher, (which has the address printed on it, having the payment taken out of a designated bank account, or you can pay directly on the IRS website. 

https://www.irs.gov/payments/direct-pay 

https://ttlc.intuit.com/community/tax-payments/help/how-can-i-pay-my-federal-taxes/00/26212

https://ttlc.intuit.com/community/tax-payments/help/how-do-i-pay-my-irs-tax-due-with-a-check-or-money-order/00/26403