bad service and no network

<p>I have been trying to get VOdacom to fix my internet connection for a month . I use an Iphone 6s and my network goes from 3G to no service. They have been calling me but not fixing my settings . They are useless and *********** . I put someone else's sim card into my phone and their simcard was on LTE and I want to cancel my contract and they are giving me the run around . </p>