Q: iPad logging into cellular to buy wifi

Your question is a bit unclear. The word cellular does not seem to belong in your question. If I understand your question correctly, you are trying to connect to a paid wireless network. Once you have paid for access to this wireless network, you should be sent an automatic e-mail with a password which you need to use to connect to the paid wireless network. The issue which you experience is that you do not receive said e-mail. Is this correct?

If so, this issue has nothing to do with your iPad, at least not directly. If you do not receive said e-mail, then either it is not being sent, or not being sent to the correct address, in which case you need to contact the owner of the paid wireless network for support. Another reason may be that you are trying to check your e-mails, to see if you have received said e-mail, but since you are not connected to the internet, you do not receive any new e-mails. In this case, it is a vicious circle; you cannot receive the e-mail with the required password because you are not connected to the internet, but you need the password to connect to the paid wireless network and access the internet in the first place. You will also need to contact the owner of the paid wireless network in this case to receive the required password in a different way than via e-mail.