Mark Davies, the Communications Director for the Post Office, said: "We apologise to our customers who are being inconvenienced by the strikes today."
He added that the Post Office's transformation plan aimed to reduce the company's losses by investing in Crown offices.
More top news
Nearly 300 staff have been axed at Russell Hume after the meat supplier collapsed into administration.
What would the Colonel say? KFC been forced to shut a number of its outlets across the UK after running out of chicken.
A former Birmingham University academic has been jailed for 32 years after abusing and blackmailing more than 40 victims online.