The few times I've called, they do have people who pick up the phone and listen to you. It's actually quite cool.
Have your story ready, and remember to be polite. (If only because a lot of MEPs really do deserve our respect.)
e.g. https://www.cnet.com/news/encryption-and-fighting-terror-hav...
This might change, but there is hope that they will continue with this position.
Since you're likely to have multiple MEP representatives from different parliamentary groups (and different national parties), it's worth getting in touch with each of your representatives by party to make your point clear. Some groups and parties will be more sympathetic than others but all will benefit from hearing this - and phone is more compelling than e-mail.
(I'm still trying to find a previous similar vote that might be enlightening on what you can expect.)