Getting their home number is a better idea.
Also as the guy above me said, if you pay by cheque you have to understand that firstly he might not have been able to take the cheque to the bank the second it came through his postbox, once he had taken it to the bank he would have to qait for it to clear and unless he has online banking he probably wouldnt be checking everyday.. So it all adds up the days, I know that when your waiting for bike parts or bikes or whatever 1 day can feel like 3.. But give him a wee bit more time!