IVR problem

I am new to freePBX. I have installed freePBX and created an IVR, so it works very well but there is a big problem, when the caller hung up before the IVR menu ends, the line stay busy and I cannot make calls (until I restart the dahdi module) and if the caller follows the IVR until the end, it works very well
so please helps me I am in trouble
sorry for my bad english