T-Mobile is buying most of US Cellular for $4.4 billion

• Telecoms giant T-Mobile is buying US Cellular's wireless operations for $4.4 billion.
• The regional carrier has been up for sale since last year and mostly services rural customers.
• T-Mobile also recently finalized the acquisition of Ryan Reynolds-backed Mint Mobile.

T-Mobile has struck a deal to buy "substantially all" of US Cellular's wireless operations for around $4.4 billion.