TPG will offer six months of free mobile services when it launches a new mobile network next year to entice customers to test out its infrastructure.

The cut-price telco surprised the industry on Wednesday when it paid a record-high price for mobile spectrum and announced plans to build a fourth 4G network covering 80 per cent of Australia's population.

Meanwhile, Telstra's share price continues to fall as investors worry about its ability to maintain higher mobile prices Analysts expect it to lose up to one million customers and are lowering their target prices.

Telstra shares closed at $4.16 on Thursday, down from $4.56 before TPG announced its plans. TPG shares are currently in a trading halt that will be lifted on Tuesday morning. It last traded at $6.66.