Hi, I started to install Avast Free Mobile security on my Samsung Galaxy, but didn't proceed with the installment as it started to ask for payment details. However I think it has installed a virus or spyware or something on my phone. I keep getting a message saying that my phone has been randomly selected for a chance to win Tesco vouchers. I can't close down the message. It tells me to Click on 'OK' which I haven't done as I think it will install a virus. Oh please can anyone help? Thank you.