The price mentioned in the signal and the actual price may differ due to many reasons
1. The entry price of a signal can be few seconds to few minutes old(depends on market volatility and the time taken by your signal provider to post the signal). This may result in different prices.
2. Forex market is a non-centralized market therefore each broker or price sources have differences between them. You can read about it here (https://hercules.finance/faq/why-prices-are-different-by-each-forex-broker-can-the-price-movements-be-different/).
3. Different spreads are applied between account types(DD and NDD) and different brokers.
4. Time delay from telegram copier to process signal. If good computer performance and network conditions exist, The copier can detect a signal and send to mt4 in less than 1 second. The broker may take another 0.1 to 2 seconds to fulfill the orders(depends on broker execution and broker server distance).By default the copier uses market entry. Which is entering at the market price as soon as the signal is received. This usually open trades closely to signal received in major forex pairs where price data do not have much deviation. However this may not be the case for non-major pairs.
In that case you may opt to use the pending order option. Where you will place a pending order at the price as the signal. However this has the risk of order not converting to an actual trade if entry price is not reached in time or not reaching that price at all.