Let $R=\mathbb{C}[X,Y]$, the polynomial ring in two variables over $\mathbb{C}$, and consider the (principal) ideal $I=(X^3-Y^2)$ of $R$.
I've shown that $I$ is a prime ideal and that it is not maximal, and I'm trying now to show that it is contained in infinitely many distinct proper ideals of $R$.
There's a theorem that states that ideals of a ring $R$ containing an ideal $I$ are in bijection with ideals of $R/I$, so if I can show that the latter set is infinite then I'm done. But I'm having trouble with this (or, well, thinking about the quotient at all).
In fact, your claim holds over any field, not only over $\mathbb C$.
Consider the ideals $(X^3-Y^2,X^nY^n)$ for all $n\ge1$.