Hmm, obviously the line is not as good as it should be, but depending on what tests the engineer actually did, intermittent noisy lines are not always detected. If he didn't do copper tests, then he wouldn't have detected bad joints etc. This is where the phone comes in handy, if there is an iffy joint or fault between one line and another, or sometimes water in it, when it starts playing up a bit, you can often hear it. Then it stops for a while, so you don't actually hear noise, but your broadband isn't good.
Have a look at your fault ticket and see if there is any detail there about a Copper Line Test (CLT) - you can post it here if you want, but don't post your phone number, circuit IDs or the agents name on the forum.
If you want to try running RouterStatsLite and want some guidance setting it up, just ask.
