Lowballed junior salary - is it even a thing?

When I started my first tech job (IN LONDON) as a bootcamp graduate I tried to negotiate my salary but I was lowballed to 30k. I knew that people hired through the same pathway a year before me got 35k. ✨But I overlooked it as was grateful for a job in a current market. ✨

After 4 months, I outperformed my current level, my manager was truly impressed and I’ve got a promotion to engineer I. I was disappointed to hear that lowest band for that salary is 35k and I cannot negotiate as it’s a promotion not a raise ✨ (doesn’t make sense but I was, again, grateful as the job market is bad). ✨

Now 4 months forward I’m getting more and more bitter about a salary. I’m doing A LOT. Contributing to a team, I’m no longer a liability. I was planning to ask for a raise after 2 more months to keep reasonable 6 months from my promotion.

But today I’ve got so angry. My company just announced an apprenticeship where people with no experience will be put through a full training and while still on training they will earn 33k. 33k?! I’m working my ass off, being very visible within company, constantly delivering. And after 8 months I’m earning 35k. Whereas new people joining with no experience will earn almost the same…

Am I being taken advantage off? What should I do? I will ask for a raise next month but should I start looking for another job? How?! I’m still junior. Does it makes sense to look for another job with just a year of experience? Am I being ungrateful?