Harassment at its best for little money

Good day, I am getting a bit annoyed with your collections department. i called in last year July and made an arrangement on my account. i have kept to the agreement every month. i got an email last week and the amount has all of a sudden changed from what it was and as per the arrangement. i then called in last week and asked that there be a note on the system for the 27th as per my banking app min payment by. so, I keep getting calls this is arrangement for such a little amount is insane. I want my call recording as i am in full right to request it.