do you need Wi-Fi to your cellphone if you have HSDPA in terms of using internet?

Answer 1

Well using Wi-Fi on your phone to access the internet through your home network or through a public Wi-Fi hotspot (like coffee, hotels, airports etc) is free and does not incurr any charges from your cell phone carrier.

However most people don't know how to use Wi-Fi and use the internet from their cell phone network such as HSDPA. This will cost you a fee from your cell phone carrier for the amount of kilobytes you use and for the data on the internet to your cell phone.