Talks between T-Mobile and Sprint for a stock-for-stock deal that makes Deutsche Telekom the controlling owner are moving forward, sources tell CNBC's David Faber.

However, some T-Mobile shareholders are frustrated with the deal price, these sources said.

As previously reported by CNBC, the exchange ratio for the stocks is expected to be at market. The deal price range continues to be locked on an exchange ratio that gives no further premium above Sprint's current value, sources said.

Shares of Sprint fell 0.89 percent in morning trading, to $7.81. They are down 7 percent year-to-date. T-Mobile US shares rose 0.21 percent, to $61.83. They are up 7.56 percent this year.

T-Mobile is owned by Deutsche Telekom while Sprint is controlled by SoftBank. The two have talked off and on over the years about a deal, including talks earlier this year. A big issue would be whether U.S. regulators would sign off on a merger of the third and fourth-largest wireless carriers or block it on anti-trust grounds.