We have a number 1 digit different from a local butcher, and used to get calls for them. Once the numbers changed from 4 to 6 digits, the calls seemed to disappear, but I never worked out why, as the same 2 digits were added to both. 
Our number was also very like the number of the manse (think 3345 against 3445) and once, when we had a minister with the same first name as DS, I had a long and confused call with someone who asked, as I thought, to speak to DS, who had just gone away to university. The caller was a bit taken aback to find that the minister had gone away until I recognised his voice and we sorted it out.
Some great stories on this thread!