I've got an Amaysim (Australian carrier) SIM that was working fine on my Galaxy Ace up until a few hours ago. The 3G that the SIM enables me to use is working fine, it's just it can't send texts or make calls. I've put the SIM in question into other phones (a Blackberry and a Nokia), worked fine. I've also put other SIMs (from other carriers) in my Galaxy Ace, both worked fine, could send texts and recieve calls fine. It appears that it's not the SIM that's the problem, nor is it the phone. What is going on here? Help please?