Typically it's impossible to recover SMS and MMS messages that have been deleted and I'm not sure I would trust any app/service that says it can. In my time here at AC I have yet to encounter a user that reported successful recovery of deleted messages.
What app were you using?
How did you perform this deletion? By what method did you do this, swiped it away, opened a menu and chose delete, picked each message, how did you delete these messages?
I found with Google Messages if the conversation is swiped away there's a chance it ended up in your archive instead of being fully deleted. On the other hand if a menu was opened and delete chosen, the messages are gone.
The only way to secure your messages is with intentional backups. Sometimes you can unintentionally get messages back by changing messaging apps. When starting some new messaging apps they will ask what you want to transfer and choosing options like, everything, or all-time, the new app can find them. It hasn't happened for me in a long time but I remember being able to recover years old messages this way so it may not work anymore.
The best defense is being prepared in this case and getting a backup service now so that it can't happen to you again. Which sucks given what you've lost but the alternative is losing something else in the future.