Harassment and embarrassment

I keep receiving calls from a company called VVM debt collector, they even phone me at Night which is not allowed. they are telling me that my account has been handed over by edgers, i then contacted edgers and they confirmed more that 4 times that my account is not handed over to VVM, i then contacted them and spoke to a lady who said she is the Junior Manager and her name is Micheal Mynhardt who promised to contact me back on the 27/07/2017. she did not contact me and i then contact her back to find out what is happening as i am still getting calls from VVM, she said she spoke to a representative from Edgars and they confirmed that my account is handed over, i then asked her how so because i also have confirmation from edgars that my account is not handed over, she then promised about 2 weeks ago that she will send me a letter from edgars with confirmation that my account is handed over to them. The most annoying part is the calls that i keep getting form their consultants that are rude, unprofessional and never willing to listen, if i do not get a response in the next day, i will take legal action against you guys, this is not a threat but a promise.