Disgusted - Switching Banks

I am a single mother that has my mom and child to look after. I was in areas 1 month. I made an arrangement to pay the areas off in equal instalments which we agreed upon. However last month the decided to double debit my account leaving me in a financial crisis... R8024 was deducted from my account leaving basically nothing for me to live on.... They point blank refuse to commit to the agreement made 2 weeks prior to that. After a terrible month and putting myself in even more debt... They now want to also take the amount that I initially was going to pay if they did not take the full amount.. There service is really bad and they don't really look after there loyal customers which I was for 15 Years.