M500 deal not as expected

Hi everyone. My M500 deal I recently just got is slower than the M250 from previously. Slow and delayed responses when using it . I have noticed many things like no more WiFi in the garden, which was not a problem before as well as around the house places that were no problem have become an issue. I spoke to a virgin media agent and they said all good on their side . Hub is working . My hub has been changed from the m250 deal to the m500 deal but location is the same as before . No changes to that and no changes to the house . Anyone had issues like this . Thanks in advance.