Scalable text frame and text

To enlarge text frame in order to create more space for typing text, click the Selection tool (V) to show the bounding box, then click-and-drag any of the corner point to resize the text frame without affecting the original font/type size.

In contrast, if you have selected a text frame with the Selection tool, to enlarge the font size, just to select the Scale tool (S) or Free Transform tool (E), any adjustments and dragging of the text frame certainly will scale the size of the text inside the frame. Hold shift while dragging will proportional increase the font size.