Landline phone company Verizon Communications Inc. has agreed to pay more than $800,000 to settle charges that it overbilled Massachusetts cities and towns for phone service. “This agreement ensures that cities and towns are repaid for losses on account of these billing errors,’’ said a statement from Massachusetts Attorney General Martha Coakley, whose office negotiated the settlement. Hundreds of local government entities in Massachusetts which contract with Verizon for telephone service were overcharged a total of $1.5 million.