Using wifi and internet

I am using wifi with my iPad through an airport extreme to a speaker which works fine except when I have wifi on I can't connect to the Internet using the inbuilt sim card. I have to turn wifi off to use my sim card. Is there any way around this?
Cheers,
Paul

Thanks for your response, at least I can now be sure it's not me doing something wrong! Pity it can't be done, I would like to listen to music through some decent speakers while working on the net
Thanks,
Paul