I paid over 12k for bitcoins and it was sent and I have a copy of the bitcoin transaction. I have not received the amount into my wallet. Is there any way that I can still retrieve my bitcoins? It has been 3 days now and they provider is one that I have used before and I trust that the bitcoins are there but I need to find a way to access them.
If your wallet is a custodial wallet where the private keys are managed by the provider, your only recourse is to contact the provider.
If your wallet is a non-custodial wallet where you manage the private-keys yourself, there are several possibilities
check that your wallet is fully synchronised. How you do this depends on which wallet you use.
check the transaction by entering the transaction-id at several blockchain explorers. The business or person you bought the bitcoins from will be able to tell you the transaction-id and receiving address (it might have been printed on a receipt, mentioned in an e-mail or in a text-message etc)
check that the output of the transaction was sent to the correct Bitcoin-address. You can see the actual recipient addresses of the transaction in a blockchain explorer. Your wallet should be able to show you a list of the receive-addresses it has generated. Wallets nowadays generate a new receive-address for every transaction.
If the sender assigned too low transaction fee it may take quite long to receive your bitcoins. Using your receive address check your transaction via blockchain explorer to see the details