Extremely unhappy over receiving letter

I received a letter from Nation Wide Recovery Services telling me that my credit card account was over the limit. This is unacceptable and extremely upsetting. I have a store account with woolies and a credit card for a number of years. In that time I have never missed a payment. I have the app on my phone which tells me the status of my acc. This is not the first time nor will it be the last time that I am over. Why must I receive a letter that makes me feel like I dont pay my acc. I have a debit order set up for my credit card so monies will be paid regardless of me being over or not. I went in to the store to pay this months acc. but I was told that the debit order would still go off even if I pay in store early. I could not move up the date for the debit order either as it was already set for this month. My reference number for this call in store was ***. This is upsetting me and rather frustrating. I have always been a loyal customer and I am extremely unhappy with this. I understand that the letter is only telling me that I am over my limit but since when does a debt collecting company do this? Should it not be for people that dont pay? EXTREMELY UPSET AND UNHAPPY.