I'm no expert, but you might be confusing throughput with latency. Speed can be measured in more than one manner.
Throughput means the rate at which mass is delivered. AKA flow. In the context of download or upload speed, it's usually measured in bytes/second or bits/second. Latency is the time delay between when an object is sent and when it arrives at its destination. Which is usually measured in "ping" (milliseconds) in the context of internet speed. For example, a bullet is fast in the sense that it has low latency, but also slow in the sense that it has low throughput. The Mississippi River is fast in the sense that it has high throughput, but is also slow in the sense that it has high latency.
The aim of upgrading your ISP is usually to improve throughput. But the ping may go up or down, since data packets are usually passed along by several "helper" servers, and the new ISP probably routes your data packets in a manner different than the old ISP. Which doesn't bother most people. Because ping only matters for online videogames, whereas most people just want to use facebook.
I only understand this in the abstract though. I don't understand this enough to offer concrete advice to lower ping. Except that it probably involves going to some obscure part of the operating system and changing the configuration settings.