Morgan Stanley downgraded shares of Verizon to equal weight from overweight on Wednesday, saying the stock has hit the firm's $58 price target and is "already priced at a premium."

"For 2019 we expect Verizon to report just 1% EPS growth ... on broadly flat revenues," Morgan Stanley's Simon Flannery said in a note.

He sees slowing growth next year in part because Verizon has made meaningful investments to be the first carrier with a 5G service. The firm says there is "more upside risk" to capital expenditures and spending on spectrum going forward."

"We expect limited 5G Home revenues in 2019 as Verizon awaits standards based equipment around the middle of the year," Flannery said.

Shares of Verizon fell 1.3 percent in premarket trading from Tuesday's close of $58.85 a share. The stock has risen more than 11 percent this year.