Check what the procedure is at your sixth form / college for swapping A-levels a couple of weeks into the year. Many will allow this, and if you're genuinely not sure, you could always do a week or two of textiles and then swap if you realise you don't actually like it.
Alternatively, you can check out Youtube videos where people show their work completed over the year for textiles or DT and see what seems more like what you'd enjoy doing (though keep in mind often the people showing off their work are exceptional A* students).
If you're still not sure, I'd say it tends to be better to stick with what you know you like.