what is I2c address of BNO055?
No, 0x70 address should not be possible. Make sure pins PS0/PS1 (protocol select) are connected to the ground, to activate I2C protocol.

Then, depending on address selection input COM3 the BNO055 address will be either 0x28 or 0x29. Decide which address you want to use and connect COM3 pin to either GND or 3.3V directly.

Also, depending on I2C API you are using, the addresses might be represented shifted to the left (to make space for RW bit). These APIs will use 0x50 and 0x52 correspondingly. Still no 0x70 in picture.