The proxy you bought is still recognized as flagged because it is being issued out of a datacenter, which is something Jagex can identify. This isn't to say that the proxies are completely useless, lets say you're botting and one of your multiple accounts that each have a proxy gets banned, this account is still separated from the others since they are under different proxies, thus preventing a chain ban. The locks are most often issued when doing Tut island. You can literally do Tut island by hand under these proxies and they will still get locked. it's a way for jagex to weed out incoming bots.
If they survived tut island, the proxies can be used. For instance, ive used them for lvl 30s, 50s, etc and they don't get locked after a botting run. But they don't prevent bans either. they just help with not getting swatted all at once.
Solution: get the lvl 3's from someone else who successfully made them. Then slab a proxy on them but these proxies will pretty much only separate your bots from a chain ban. If youre suiciding tho, i would use multiple bots per proxy since they will get banned anyway.