Billing violated a payment arrangement by cutting off my services, which required me to make a payment before I was suppose to

I had an installment agreement to make a 2nd and final payment $255 on 1/31/22. I was also suppose to get a $100 credit that I don't see. I had to make a payment to get my services back on, yet I see they still have the payment arrangement of $255 for today!!! It won't allow me to edit the payment The account specialist promised my services would not be cut off-----if I have reconnect fees for this error, they are going to have to remove them because they are breaking the payment arrangement big time. The chat option is absolutely useless and just asked me the same question about what service I am wanting to look into over and over again! There is no email option, what company does not have an option for customers to send a message????  Perhaps they don't want a paper trail. I hope customer service is ready for my call today. I have been an At&T account since they were Cingular---more than 20 years and I think this is the final straw.