multi pppoe per one ethernet

Dear Sirs;
simply my case is i was connected to isp then moved to new isp , i have a RB450G put all my pppoe username and passwords in it then route each one to it’s pc .
the new ISP seems look the pppoe with MAC , so now i can not operate more than the number of ethernet in the routerboard .
this problem never happen to me with the first isp .
is there a way to give each pppoe different MAC so i can run more than one pppoe per ether ??? , by making tunnels or what ever even if i have to put two RB in series .
will be waiting your instructions eagerly .
with best regards .