On TV, a speaker said:
en plus de ça
I don’t remember the whole of what he said, but we can imagine an example like this:
J’ai voyagé partout et, en plus de ça, j’ai été payé pour me déplacer.
I travelled everywhere and, what’s more, I was paid to travel.
When the speaker said en plus de ça, he used an informal pronunciation. What he said in fact sounded like this:
en plus de t’ça
If you want to try to pronounce it yourself to hear how it sounds, here’s how to do it:
First, say de aloud. Now say de with a t sound on the end of it. Now add ça after that. That gets you de t’ça.
Now you can say en plus de t’ça, where plus sounds like plu.
This informal pronunciation of de ça as de t’ça isn’t uncommon at all. You’ll hear it frequently in informal conversations. It can occur whenever de ça is used, and not just in the expression en plus de ça.
That said, you don’t need to adopt de t’ça yourself (de ça is always acceptable, even in informal conversations), but do learn to recognise it.