Function crBold is to be used with Conditional formatting only (those X+1 buttons on different windows).

You want to format parts of the text with different formats. To do this, you need to build your text in Text Object instead of Formula Field.

- Add Text Object to your report (Insert | Text Object)
- Write static texts - in your example: T[space], F[space]
- Drag {telephonenumber} from Field Explorer to Text Object after character T
- Drag {faxnumber} to text object to its place

And to format letters T and F:
- "paint" T and click Bold button on Format Toolbar and repeat this with F