Changing IP on a T-Mobile Wireless dongle

[ihatescams]

I have recently noticed my IP address changes less randomly than it used to.
For example an IP of 175 . 234 . 69 . 84
Changes to 175 . 234 . 12 . 79



Is this enough of a change to stop ebay tracking my IP address ?
Do i need to change the whole thing or is it stealth for only the last two digits to be different.

[ihatescams]

Please help guys , i give alot to the uk forums , all i need is confirmation that the above example is ok