Xbox 360 live unplayable being accused of...

Question

hi i have been online playing pro evolution 8 and also fifa 08 for first few days everthing fine now every time im playing screen will freeze restart in different place and eefects both players i have re setup my link checked my laptop and played games off line to check console both in working order what could be wrong im totally lost. called xbox they were useless treated me like a child and still havnt called back 48hrs later after they said they would. please can you help1 i am paying£4.99 a month to be member