BT is raising the cost of phone calls by 10% and the monthly line rental charges by 50p from October.The telecoms giant will this week write to customers telling them about plans to up the cost of connecting a call from 9.9p to 10.9p and lift the daytime rate to 6.4p from 5.9p. BT reckons the changes will cost most people an extra 1p a day, while anyone who signs up for a one-year contract will avoid the higher charges.It's all part of move designed to get customers to sign up for longer term deals and special bundled packages that offer cheaper rates.A landline will cost £159.48 after 1 October, but will be £131.88 for those that pay everything upfront and just £113.88 for anyone who signs up before the end of October.