MFC CHANGES AGREED EXTENDED PAYMENT TERMS A MONTH AFTER APPROVAL!!!

Extremely angry with MFC they extended my payment till the 31.01.2021 on the 19.09.2020 and now i recieved a statement on the 17.10.2020 (A MONTH LATER) whereby they have gone and amended the agreement and changed it to the 31.10.2020, they expect me to make a payment without any communication with me whatsoever of the changes that they proceeded to do. If they were not meant to extend my payment break why did they agree to it and update my statement in the first place? Their mistake is not my issue or fault. I recieved a salary cut and told my company that i will be able to manage till Janauary as MFC as extended my terms till the 31.01.2020, please explain how they can just go and change it just like that without advising or communicating with me at all regarding this?