Sterns do not value loyal customers!!!

I am disgusted with the manner Sterns treats its loyal customers. I have an excellent account record with Sterns and have had this account for over 20 yrs. However in December my instalment was R1835 but since I did not have my statement on hand, pd an amount of R1800. On Monday 11 Jan I received a sms from Sterns indicating that my account is in arrears and that I must pay an amount of R1870 urgently to protect my credit record! I am furious that they send such an arrogant sms! Today I get a call from the sterns head office demanding I pay R1870 immediately (January's instalment as well). This is not in keeping with the CPA?!!! I was furious and requested to speak to the supervisor (Elliot) who was not very helpful at all. All he could say is that their system is such and also asked me when I can pay the R35! The audacity of him! He mentioned that the sms must have been sent in error and apologised. But then why waste time calling me to pay R35 when they can just add it to my next instalment! Sterns must appreciate their loyal customers - that's why they are still in existence!!! They need to customise their IT system. This type of treatment encourages me to close