What you want is the situation to improve. Talking to your current sales rep could work, sometimes you have a little motivating to do. Changing the rep could work too.
And you are not stuck, you have strong incentives to stay. Which is different.
Once incentives to change mount up, change can happen!
And dissatisfaction with a supplier/service provider can even make people switch to an inferior solution, if they get better treatment there.
I used to work for prediction provider (certain topic of predictions, not general). For some subtopics we were great, for others not so much.
One day, we rolled out an upgrade which impacted stability negatively. I personally advised for rolling back, but the new features were deemed strategically important to acquire new customers, so the decision got made to not roll back.
Users groaned. We worked on improving stability, but it went slow. Users groaned so much their bosses listened, and SLAs got checked. We were within in the limits of the SLA, but we used up our yearly allowance in 2 weeks! (Luckily for us, it was in December).
Then a big customer cancelled their contract 1 year in advance and told us: Either things improve drastically, or this cancelation stands!
This finally got the attention of our boss and priorities shifted.
So this worked!
In the same company, we were so dissatisfied with our database provider, we switched them out. It wasnt highest priority, but they worked on it for 5 years! Little by little. Their reps never got alerted to that fact, the dissatisfaction was that high.
So, if you are dissatisfied enough, switching may become suddenly an option. Even when it's costly. So you have still some leverage.
When you call with the rep, you dont have to go nuclear right away. Simply stateing your dissatisfied and want things to improve may be enough.