My partner took a contract Phone Samsung A35, which was R400 every month

My partner took a contract Phone Samsung A35, which was R400 every month. Everything was going well until this year. The bill started to go up, and they wanted him to pay R3000, when he called them to ask about the R3000 bill and they told him that I overused the data and minutes and they also told him about the subscriptions I never took, cool he payed them that R3000 amount and told them to close the top up and the subscriptions. This month again, they said I overused the data and minutes and which is a lie because they have turned off the top up and I don't understand because I'm always using Wifi, they want him to Pay R600 for calls and R751 for data which is R1351 for last month, and they told him that the bill for this month is already going on R1000 and that time I haven't finished my free data and Minutes and again I'm using wifi. Isn't this a day light *******? I believe they are ****ming him.