Here today gone tomorrow

Ive got Uncapped Adsl at home and use the data bundle for cell, ive had a few times now that my line has been down or very badly slow. the whole day my internet has been down on cell and so ive had to switch to my MTN data and buy more data for that. Why do i then pay for a service just to have to buy more data elsewhere? Im at my end and looking at other options for internet, what was once a great service is steadily going down the drain !