How can I fix a problem with the water dispenser in my Samsung FF RS2iDCNS ?

We had a problem with the water dispenser. We could not get any cold water. It appeared that the water in the pipe was frozen, so we switched off the Freezer section and lowered the temp. to 16. We removed all the food. After 24 hours the water started to run again, but 24 hours later the same thing happened, so we went through the same procedure again, this solved the problem temporarily, then 24 hours later the problem was back. We are now down to -15F, which is only one degree more than the suggested minimum. What is the problem?