Vodafone Internet Issues: Slow Speeds, Many Excuses

I have two Vodafone phone lines, and I'm paying a lot of money for both, but I can't use the internet on either of them. Every time I talk to a customer representative, they always come up with different excuses and blame things like the phone, the line, or the plan. I got a new phone, got a new phone plan, and even switched plans like they suggested. But my internet speed keeps dropping from the promised 5 Mbps to a really slow 100 Kbps or even 10 Kbps, and sometimes it doesn't work at all. It's really frustrating. Even though I'm supposed to get at least 5 Mbps, I'm not getting the speed I'm paying for. If this problem keeps happening, I'm really thinking about switching my two phone lines and my family's other connections to a different provider.