DSTV PRICE LOCK

good afternoon, My mother is a pensioner and very sensitive, she s been receiving calls from this number ***. in the past months they changed her decoder to dstv explora price lock, she s been paying the monthly payment to the amount of 420 and now she receives the calls that she must pay an amount of 159 to Absa account and they also debiting on her bank account. please i need clarity how does this price lock works and the exact amount to be pain. her id number is, ***. NJ Mazibuko