I'm not sure which membership texting "MONTHLY" to 1745 buys you. It used to be Standard/€10. You may still get that if you still qualify for Standard membership. However if "MONTHLY" bought one membership and you then bought Don then the first membership will take effect and only when it has expired will the Don membership kick in. That's how 48 membership works. Buying a membership does not prematurely terminate an existing membership and kick in immediately. Any current or stacked memberships must run their course first. You could always log a support request to ask 48 if they can do anything for you in this situation:
http://help.48months.ie/requests/new
If you are stuck with the current membership and the stacked Don membership and need internet access then you can buy an internet add-on - €3 for 750MB for a month.
http://community.48months.ie/t5/Need-Help/How-do-I-buy-stuff-by-text/m-p/118#U118
http://48months.ie/deal
Hope this helps.
