They Do not honor guarantees

Very disappointed , I Bought a Expensive tester from them, this tester Was faulty from the start , i took it back the 1st time , they said No problem because i have a life time guarantee on that tester, so they Gave me a new one, The tester started giving me the same issue as the previous one about a year later , I sent it back to them only to hear that they no longer sell those testers and cannot Honor the guarantee , this is totally unacceptable , the reason i bought that tester was for the lifetime guarantee and the features it had. Now they just chase me away and say i must try another repair place??, They Sold it to me and boasted the guarantee , they should honor it , its not my problem they do not sell it anymore. They could have offered me a Suitable replacement but just shunted me away...I need this sorted out ASAP so we can avoid legal actions.