Poor customer service

I’ve tried making a payment on the 30/01/2024 however the app kicked me out , this morning I got a message stating that my payment was unsuccessful bare in mind I have sufficient funds in my account . I’ve emailed pay just now regarding this matter however they not willing to assist , I’ve been a loyal customer for 3 years and this is the type of service I receive . I refuse to pay a penalty knowing that I have funds in my account . I’m very unhappy about this whole situation and they clearly not willing to solve this