Misleading Information and bad service

I took my phone for battery replacement and screen replacement on Monday the 1st of February 2016. A gentleman with the Danny told us that it's gonna cost me R900(this was due to 2 jobs to be done on the phone)I left the phone and asked for an invoice. He said to me I'll get a receipt later When I pay and the job is done. He later called to confirm that the job is done and I can come collect my phone. When I got there I was told he is not there and don't know how much I was gonna pay for the job done. I told them he said if he is not there any of the staff members are gonna assistant and it was only then then the guy was willing to help. When I was still waiting then this Danny fellow came and printed a receipt and it was reflecting R999.99. When I complained and asked for a manager he then called someone and spoke in Afrikaans telling them that I am not willing to pay R999.99. He then said to me the manager said if I'm not willing to pay R999.99 the'll will then take out the battery and screen and put back the old parts and security guard was ready to embarrass in front of everyone. This is totally ********* and unacceptable and I think it is against CPA