Charge for installation because of low credit score ? Where do you get these credit ratings from ?

Today I called in to apply for a voice line to be installed at my home address. The lady I dealt with was friendly and app**** for a line rental and gave me all the necessary info. However she informed me that a fee of R737 was to be paid before a technician comes to install my line if my credit score was low. I have no idea where they get this info from?? Previously i had aapp**** for a mobile phone contract and was declined for the same reason, yet in that same month i received vehicle finance. I have a house on my name, 2 phone contracts, an Edgars account, I use my credit card regularly and pay off my accounts before due time and still ??? Credit history too low? When I asked who I could speak to in order to find out the reason they could not give me any name number or email address. I would like to get to the bottom of this as soon as possible as I am not prepared to pay this amount based on incorrect credit history information.