Pressured into signing up and then the agreement changes

I am writing to express my extreme dissatisfaction with the service I have received from your company. Despite my initial enthusiasm, I have experienced a series of unacceptable issues, including:

- Three changes to my installment amount - Poor customer service over the phone - Failure to negotiate an affordable installment as originally pitched - Lack of due diligence in collecting debts from creditors

I felt pressured into agreeing to the sales pitch and the start date,without fully understanding the terms and consequences.