Any service inside of your hedge/fence/ boundary is your responsibility. Why should the rest of us pay. But don't dispair, it is easy to fix.
Get two bits of metal coathanger and bend into L shapes and hold one in each hand, walk across your garden, when the coathangers cross over your pipe should be below the ground right there.
Dig a trench the full length of the pipe and wrap pipe with insulation. Fill back the trench mixing the soil with some well rotted manure and plant a line of pansies along the line, this will help you finding it again, because if you have to ask how to lag a pipe you will most certainly will do it wrong and will have to repeat the exercise in a few weeks time.
Now this is all bulls**t as your pipe must be less than 12 inchs under the ground to freeze up. look elsewhere for the problem.