Do you drink the tea more as a preventative or only when you're actually feeling bad?
Chamomile actually does have anti-inflammatory and antispasmodic properties that are scientifically proven - so it's not just placebo. The active ingredients help especially with mild stomach discomfort, cramps, or bloating. But if you have acute, severe pain, the tea probably won't do much for you, I'll give you that. With chronic or recurring problems, regular consumption can definitely help soothe the stomach lining. Though you sometimes don't notice that until a few weeks in, not right after one cup.
The thing is, a lot of people expect tea to work like a painkiller right away - it doesn't. Chamomile works more subtly and supportively. If you really notice it's not helping, it could also be that your stomach pain has a different cause, where chamomile just doesn't help. In that case, I'd rather see a doctor to figure out what's going on. The Sonnentor package isn't wasted anyway, but I wouldn't see it as a universal solution either.