Calling mobile numbers

Question

When I dial a mobile number the display on my phone shows it ringing, but there is no audio ringing sound and when I have checked the phone being called there is no record of receiving a call from me. If I dial a land line number the phone works perfectly. This problem has only just happened today. Very occasionally I can ring another mobile number successfully.Please help! Thank you!!I have a Motorola Razr V3I