Hey - See if the same SIM card you have in your ZTE valet will work in any other phone - if it does not, then you will have to contact your Wireless service provider's Customer Service Centre for an account on the possible cause (do ensure that FDN is not active on the SIM card first). If the SIM card works in any another phone, then make sure Flight Mode is not active (checked) on the Valet - to do this, go to Settings > Wireless and Networks > Flight Mode... Also Go to Settings > Applications > Manage App > All > Phone > Clear cache ... and retry. Please do comment below should you require any further assistance on this.