Very, very poor and disappointing service received from Cambridge Open College - online courses!

On the 2nd of August I enrolled for a online learning course, Early Years Foundation Stage Practice, through Cambridge Open College. I paid an enrollment fee and chose the option to pay the balance of the course fee over 3 months. I used a credit card to pay the enrollment fee. After receiving access to the course material, I compiled Assignment 1, which I submitted on the 25th of August. Only one of the 5 assignments may be submitted at a time. It has now been 20 working days and I have not yet received feedback on Assignment 1. The course must be completed in 12 months, but the delay in assignment marking may just lead to you not completing it in the 12 month period. Furthermore I have continuously phoned the college on the contact number provided on their website as well as the student portal site as I need to make arrangements for the balance of study fees to be taken off in the next 3 months. One number stays engaged and the other one indicates the voice message box is full. I have logged tickets to the tutor and the student support desk regarding payment and feedback on the assignment. I received one reply initially indicating payment of the balance of fees to be made via "gocardless". I got a link to set up this functionality. After many attempts I phoned the "gocardless" help desk, just to learn that the functionality may not be used for South Africa. At this point I have not received any joy from this institution and feel they are poor in replying on any message sent, they cannot be reached on any contact number and they do not keep to the arrangement of maximum 17 working days for assignment results. The claim a full refund if you are not happy with the course, but how do you claim your enrollment fee back if you are not able to get in contact with them? They should not be supported as a online learning institution. You will be wasting valuable time and money.