I don't know why internet providers don't value their existing customers, offering only the cheapest deals to new customers, but you can play hard ball with them.

1. Call them within the 30-day no-exit-fee cancellation period and talk about your contract ending
2. Wait for them to offer you a shitty deal. Sound disappointed, make sure they can hear you clicking and typing, and talk about looking for other options instead. Thank them for their time, and amicably end the call.
3. Wait a few days.
4. Someone will call you back and offer you a less shitty deal. Make it clear that price is the main issue, and express interest in their slower packages. Get them to go as low as they can possibly go on a slower package. Sound unconvinced.
5. Start lamenting about the current package, wistfully talking about how you wish things could remain as they are and that you don't want to keep changing providers every 2 years.
6. Wait for them to offer the best shitty deal on your current package, and express interest. If they refuse to budge any lower on price, get them to throw in an extra like a public IP4 or something.