Dum Struck Vodacom service

I am writing this on be half of my sister who received a Samsung S8 for Christmas in DEC 2017, this phone has been giving her endless problems of which she has taken it back 3 to 6 times back and forth to Vodacom empangeni and Richards bay only to be told there is nothing wrong with the phone!!! I my self own a Samsung s6 edge and am no expert however i can see there is numerous this wrong!!! eg:. the pictures don't always open, the phone freezes data gets lost it even restarts on its own etc she has taken it back within 7 days of which rightfully in the contract says you are allowed to get a new 1 but they kept rejecting and saying the phone is fine but actually till now the phone is not fine and does not work to to its full potential. Vodacom's service has dropped drastically and they do not live up to their promises neither does the contract hold any advantage but yet they are quick to deduct their money every month!! We spoke to so many people at vodacom and all of them are dum struck as they cannot see the phone is faulty sometimes things don't wana close. it even has errors on some apps!!! for a new Phone one would think it should work well but nope it works like a refurbished phone. Extremely disappointed in this type of service i'm hoping you will contact her with regards but i'm sure you to will find fault so you don't have to be liable to replace an expensive worthless phone, its worthless if it cant work yet you continue to deduct your money!!!